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ESTIMATINGPREMORBID INTEWGENCEUSING THE NATJONAlADULTAEADINGTEST

IN NEINFOUNDLAND

Karenlynn Sharpe,S.A.(Honours)

Athesis submitted tothe School01Graduate Stud iesInpartiallulfillment01the

requinlme,,;s01lhe degree of MaslerofScience Department01Psychology MemorialUniversity01Newfoundland

August,1990

CopyrightC1990 Karen lynn Sharpe

Newfoundland

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ABSTRACT

The~118bllityandvalidity

or

the National Adult ReadingTest (NART. Nelson,1982). a mellsure ofpredic tedpremorbld Intelligencelevel,was a.amlne<!. Subjectswere twentymild·

moderate demernlng (17lemal". 3 males) end twentynondementll19(14Iomales , 6males) Individuals aged59·69.The NART demons tra ted high Inter·raterreliability(!'•0.96 ,1!<.001).

Tho NART was avalid measure of Intoll1genc:eInthaiitOOfrelatedwell will i, andpredicted a substa ntialamou nt of varianceIntheWechslerAdultIntelligenceSCale-RevisedFullScare o(WAIS.RFSrO)andVerbalIntelligenceQuotient! (WArS·AVIC)In thece neetsample. The NAATwas retatlvely "dementia-reslstant" In that NAAT per10nnancadid notsignilicantly correlate with severityofds mantlewhen the demogr aphicvariab les werepartialled out. Further,Itwasthe onlyoogn ~lvemeasureon which therewasno signi ficantdifferencebetween deme ntlng and controlsubjects, when the demogra phicvariableswere partialled out.Reg ression equations10 prEKlictdementing subjects'premo rbidWAIS· RFS1Qand viafrom NARTerrors (NART FSla and Via) andfromWAIS· RVocabulary age·scaled scores(VocabtJlary FSIO and VIO), ware developed usingdatafromthe control SUbjects.Predicled NARTFSIO and VIQweresignificantly more'dementia-resIstant" thanpredictedVocabUlaryFSIQand VIQ. That Is,posthocSchetfa tests revealed thatIheNARTpledlctod sIgnificantlyhigherWA1S·R FSIQ s and Vlasthan the VocabularysubtastofthaWAIS-R(2,<.OS). Demograp hic variables didnotadd aslgni ~eant amountofpredicted WAIS·A FSIQ variance when combined with eitherNAAT (4%)or VocabIJlary subla st«t%). TwoWAIS-R algorithms wereinvestigated Inmelrabilityto distingUishdementinglromnondem entlng indlviduels.Coolidge'salgorith m(VocaboJlary age- scaled score~2 BlockDesign age·scaledscore-dementia,Coolidge,Peters,Brown&Harsch, 1965) correctlyclassifiedastatistic ally

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<.05) butnot aclinically significant proportionof subjects, andtheV-P Split (WA1S. Rvia ·WAIS·R PIC) did notsignificantly distinguis hbetween damentlngandcontrol sUbjects, indicating that these algorithms may notbeclinic ally usefulin Identily lng dement ia. The resultsofthe presentsludyindicatethat the NAATmay be the procedureof choice for differentialdiagnosisof dementiaInNorth America.

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"'

ACKNOWLEDGEMENTS

A great (toll your(!IIplealMl)Scottish"Ta" is extendedtoDr.Ronan O'C8noll for hi"healthy Type A.IIrca9lJcaJIywilly,bulserioualymatchless lupervlslon.

Iwould a/so tlke to extendmyapPrllClatlonto my committeemembers, Drs.Mike Stones and arehemSkanes for theiruseful sU{jge,tlons,butIn particulartoDr. Skaneslorhis equally slllirlcalyet immenselyastutesteuetee!knowledge.HisNewlla-Ism Iscompromised onlybyhis InabilitytodrinkSCreech.

This thesis woolcf nothave been possible withoutthe helpofthe peoplewhoreferred subjectsto the study (Drs.Harris,Strong,Eaton,andButler,Ms.lee StonesandMs.Debbie Howard),andIndeed.orthe subjectswhoparticipated. Thankyouall foryourInlerestIn edvanclngsclentlf.cresearch.

lowe my SllnilytoMichael, and my gratitUdeto Sue, both ofwhomhUngarounddespite bad moods, badbreath,and bad grammar.You're the best.

Finally,Iwoulcllike tothank theMemorialUniversity School ofGraduate Swdles tor financial aidthroughout myprogram, in theform01 Univer1ily Fellowsh:p s, Teaching Assistantships, andAesearch Asslstantshlps.

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I,

LIST OF TABLES

Table1:Dernograpl'licInformationByGroup Table 2:GroupComparisons on C09n1ltYeM• .,ures Table3:CorfelatlonsBetween&IIVaril bIM brTOfaISampllt Table4:Carrel.tIonaBetweenallVarlro bles for Control SUbiects Table 5:CotreIatlon3BetweenaMVarllblestorDementlng Sub;ects Table 6:RepeatedMeasuresANOVAComparlng Three Mu suras ofFSlQ Table 7:AapeatedM"a sures ANOVACompa ringThree MlnurnofVIQ

43

...

48

4'

SO 53 54

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..

LIST OF FIGURES

FiguN 1:Irat-Rat«R4tHablllylotNARTEnwScotM

..

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Dementia IsdescribedIn the revlMdthird edition of the D1agrmUc and StatistICal Manual of Mental Disorders fOSM·'11·A}u having the l8aturesof •...lmpalrment In short- and long-term memory, associated withImpalnnentIn abSlract thlnkll"lg,lmpair8djudgement,otherdlslUrbances 01 hJgher cortical lunctlon,or pel'!Onality changa ...OotmenUamaybeprogreulve.stallc.or remitting· (American PsychiatricAssociation,1987, pp.103-'04). Much research has been carried oullnvest!gatingthe etiologyand medical diagnosis 01demantia, however an exhaustive review...~:lnotbeundel1eken In thisthesis. A briel overview 01 demenllawillbegiven,derived lrominformetion provided in 8 recent review paper(lalit & Zent,1983).

The cognitivechanges lIIIIen In dementlngIndiv iduals are pre9Umed tobedueto atrophy througnout the cerebral cortex and are not related tothe normal aging proc8M (Zarit & Zarit.

1983). The two major Iypes 01dementia are DementiaoftheAlZheimer's Type (DAn and Multi Inlarct Dementia(MID), comPflslng an estimated600/0and10-200/001 cases 01 dementia in people over age 65, respeclively.OATis charaeterizMbyabnormal struclures In thebrain includingsenileplaques, neuroflbrlflarytangles,and gr8nulovasculerstnJcluresviewed on autopsy,and its courseIs typicallyII gradual progression01deteriotatlon.MID occurs when an individualundergoes a series01 small strokes causedbypieces ofplaque on altery Wills breaking ot! andtravelling to the brain.and there thtiy occlude c8rebl'al blood lIow,resulting In neuronal de'Jth.The coorse of MIDIs stepwise.The etiologyollhese types 01 dementiaIs unknown. Theories01 OATvary!Yomgeneflc,tc viral,to blochemicel, while MIDIs purported to berelated to the samo risktactClnlUstroke or myocardialinfarc tion. However,thereIs no clear explanation astowhy the risk lactors produce heart disoaseIn one person and MID in another.

DementiaIseasilyrecognizable In Its leter Sleges duetothe Vagtdisturbances in behavior and cognitiveIunctl1nlngthat occur,but Is alten difllcultto dlegnoseatthe beginning 01 the process. In Iact, dannite medical diagnosis01 dementiacan onlybemade et post-mortem (ZarK

&Zari!, 1983). TheComputer AxIal Tomography scan (CAT scan) wasinitially viewed as a promising1001for the diagnosisofdementia since It can detect cortical atrophy and enlargement 01 the ventricles and sulci In the brain. However. resoarch astothe utilityOf thisinst rumentIn elSeulng dementia has revealed that some degr" ofcortical atrophy can occurIntno norm.1 elderty who demonstrate no cognitivelmp.irment, end some clearly dementing Individuels do not produce positivenndlngs on the CAT scan.

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Sinc. definite medical dl.gnoMS or dementla .... Impossible, and since cognitIVe deterloreUon In dementie aP9ltarsto beuniversel and Is usuallytheimpetUs for dementlng petlentll to cometomedicalattention,I~sean::hershave attemptedtodevise psychometric m"'asu ...stoaid diagnosis In the early stagM ollhls disorder.Id.ally, clinicians would have a measure of cognitive function tak.n

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^time^priorto the development 0'. dementlng process, In which case the patient's premorbld cognitive stalUs could be compared with hls,ther current leVe' 01 cognitive lunctloning. Howeve"thisluxury sekklm eltlsts In clinical practice as many dementingIndiv(duals experiencetheir lirst visits10 psychiatric setting sonly afle, the suspected dementlng PfOCessl1u begun. TI1erelore clinicianshave attempted to estimate premorbld levels 0' cognitivefunctioning, using lestswhich have beendubbed "dementia·lnsensitlve' or 'dementla.re5istanr inventories.11Is,01 course,unlikely Ihat any psychological test willbe completaly 'dementla·lnsensit lve'dua totheimmense cortical change which takes placein the latter stages01 dementia. Thereforethe following discussionwilt be concerned with relll!l\/.

rathertl1an absolute 'dementla·insensitlvity".

80m3 01 the earliestmethods usedIn clinical practice lor distinguishing dementing!rom nondementlng IndividualsIncluded Wechsler AdultIntelligenceSCale(WAIS) or its r....ised version (WAIS-A) algorithms.The WAIS(lNAIS·A algorithms were based on ttle premise that dementlngIndividuals wouldpertcrm more poorly on some tasks

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I1old' tasks) ttlan on ottlers ('hold' tasks),while nondementlng Individualswould do equally well onboth.The "no hold" tasks were purpoJtedly detrimentally Inectedbythe dementingprocess while lhe"no nold' tasks were purportedlynot delrimenta:1y arrectedbythl dement:ngprocess. The'no hold- tasks generally (nvolved Iflamlng/manlpulatlngnew unpracticed Information.while"hold" tasks generallyInvolved more automatic or over·learned tasks, usualt)'ver bal. Alarge discrepancybetween 'hold" and 'no hold" task'swupurpoJtedtoindlca!e organicity.Some suppoJtforthis assumption has been IoundIn that some tasks (e.g.,theVocabularysubtesl 01the WAlS/WA1S.A) have been olmirved to 'hold",betterthan others (e.g"the BlockDesIgnaubleat. 01 the WAIS,nNAI5-R)In dementll (e.g.,CooUdge,Peters,Brown&Harsch,1985).

The A1S8alChthat hasbee"carriedout to determinethe accuracy 01 many 01 these equallons has been disappointIng(Vogt&Heaton, 1977).Some 01 the more successful and well·researchedmethods of distinguIshingdementlngfromnondementlng Individuals havebeen

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thOse professing to estimate premoroldIntellectual functioning.ThatIa.If one can prediclthe leve' olcognitlve t..snctlonlng before the disease plOCIIUbegan,th!sestlmatecanbecomparedto a measure ofeureeetcognitiveability.If the discrepancy Islarge enough. dementia IsstTOogly suspected.EquationshavebeenderivedfromIljtgenormative samplesbyrepresslogscoreson purported "dementlll· rell istant-variables.or melUtlreson whichd~tfngIndIViduals are expectedtoreceIve9COl'essimila r tonondemen1ingIndividuals,p.e.,demogrlphlc: Information, wordreading abllities,or theVoc abulary sublest 01theWAIS orWAIS·RI, agelnst measuresof current lmelligence (typicallytheWAISorWAIS·A fullscale Intplllgance quotients(FSlal,vertlal Intelligencequot~nts(VIa) and perlormance Intellige ncequot.e nt:t(Plan.Individuals'sc"res on the chosen"dementia-res istant' measures,arethen enteredIntothftstandardized equaUf'Jnsto determinea premorbld10 score.Ifthepredicted premorbld10 minusobserved10 dlscreplll,ICYIs large enough,dementi a Issuspected.

Earlydetectionof dementiaIsImportant totheclInicIan because first,Itallows a diagnosis thus anexplanation01 behavior.SecondIt allowshim/hertoimplement treatment qulcll1y for treatablacases. A recent review~aperoutlined treatmemdirectionslorthe subtypesof demeune which spannedfromcholitlesterese Inhibitors (e.g.,tetrahydroamlnoacridlne) tocontrolling hypertension(Whalley,1989). Whalley (19&9) concluded thatat present mere arenoconfirmed effectivedrugslorthe treement01dementia,bUtencouragedapositIVeoutlook lorthe futura.

EarlyInterventionwillbe CNclallnnewtreatments,asIItl'leyaretoworktheywill have10doso beforenecrenel death occurs.Third,earty detection 01dementia allowstorresoarchInto possllM treatments.If researchIstocontinue, aocura\"dlag nose~ofdementla are required 10 ensure researchersare examininghomogeneous groups. Fourth,untreatablecases m4Ybenelftfrom programsaimed at slowing the dementfngprocess.Finally,detectionof demenllaprovidesa gauge of howfar the diseasehas progressed andhowlast ItIsprog ressing,thus allowingthe clinician 10givea prognosis.Thefollowing willreviewthe literatureOf'lpsychom81ricmethodsor dlsltogulshlngdementlngfromnondementlngIndividuals.andwillnutlinethe hypothesesfOr a study attempting to a!lS6SSthevalidity of IheNational Adult AeadlngTesl (NART),apurported melSu re ofpremorbldintelligence, In Newfoundland.

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1.1.WAISf'NAIs.R Algorithms 1.1.1.DeteriorationIndlce.

Several researchershaveproposedWAISalgorithms fordisc riminatingcerebral dysfunction from normality (fo rreviews88a Savage,Britton,Bolton& Hall,1973, Vogt& Heaton , 1977).Thealgorithmsere all based on thef..,dlngthat someWAISfv\lAIS·Asubtestsrho~")are 1e99"dementia-S&n9itlve' (i.e.,dementl ng Individuals show less01aperlormanc:e decline In comparisonwith nondementlngIndividuals)thanothers,the'noho;';'-ubteets,which dementtng Individuals havegreaterdifficulty perlonnlngthan normal control sub}ects. Therefore discrepanciesbetween 'hold" and'nohold'sUbt~tsshouldprovide an Index 10 distinguis h demenllngfromnondementlngindividuals.

The/Irs!WAISalgorithmwasWechsler'sdeteriorationquotient(00)which was determlnecl fromthe Wechsler-S31levtJescale (Wechsler.1944).It divided"hold' minu s'00hold"by 'hold' eubteata multiplied by100(Wechsler,1944). The "hoW subtes1tlIncludedComprehensio n, Information,ObjectAssemblv ,andPicture Completion.It.nd thesewere purportedto beleast sUSC9ptlble10 cognittvedeca y.The"00hold" subtestsIncludedO~1tSpan,Arithmetic, Digit Symbol.andBlock Design.and we repurportedtobemeet susceptible re cognitive decay.

Wechslerlater revised his DO loruse with the WAIS (Wechsler,1955)andsubstitutedttle VocabularysubtestlorCom prehensionin the'hold' eubteete,andSImilarities tor Arlltlmetic Inthe 'nohold'eubteete.Useoftheselotm ulae,however,produced botherrors01commission.ncl ommlsslon sincethere werewidevariationsamongIndividuals. For example,sincethe"hold' tests have a )ergevarbalcomponent, cognitlvely unimpaired individualswhowereprollclenfat verba)tasksbut poc.r&1perfOlTJlancatasks,received a 'dementing"profile.

An early studycomparEKlthe ability01 WArS-derivedformulae(e.g.,Wechsler's 00)to identify organicityIna comp arisonotacommunityaged sample

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29) wilh a groupof dementlngIndivIduals

ill -

42,Savage et el., 1973). Tha resultsdemonstratedthatthe dlscrmlnlltoryabilityof mostof the lormulae was poor. OfperncularImportance,II thehft rate washigh,thenumberof falsepositives(controls categorizedas dementing)was also high. For lnet erce,usIngHewson's eight ratios in which eIghtWAISequationsidentifyC1Jt·offpalm

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Ind ica~ ngNeuroticv,. Normal,vs. Organic,'...8.6%01dementin g:subjeClSwerecorMClly claufflad, bul38.0%of controlsubjectswereelso cteulnad as organic. Savage and hi' colleagues'(1973)be3tclass ification syslem was the revisedWech!ller 00,buteven using this Index,thehitrat e ' Will faIrly low(52.3%)andasi.l:eable plOponionotcontrol :subjeCt! were misclaaaified (6.9% ).

Asecond sludy comparifI!J varlous Wechslerdeterioration Indlce,using II largesample of 117 neurologicallyImpaltedIndividualsvel'3Us 116non·lmpairedIndividual" alsoreported disappointing finding,(Vog'&Heetcn,1977). Vogt and Healon (1977) foundthat althoughall Indices exceptone exceededthe chancelevelslor differentia ting the gfO'JpS,allmeasuresell.cept two(Hunt, 1949 andHawson.1949, chedInVogi & Healon, 1977) mlsclassil led large numbers 01 unimpairedIndividuals asImpaired . Funhltr,the reSBalt:hersusad patientswith extreme Impairment whichtheyIndIcated probablyresultedInliberal estimates01 theWAISIndices' abtlitlestodiscrim inatethe groups,and~the Indiceshadonlylim ited successIn theirability10 discriminate.ItIs likely that had moremUd/moderatecasesbean used,whichIs the population with which eeee Indiceswouldhavethemostclinical utility,thereeeercherewould have round evenlessimpressive t'9sults. Vogt and Heaton (1977)themselvesconcluded thai eventhemost successfulIormulaeas determ inedby their study (Hunt,1949,Hewson,1949,clled InVogi&

Heaton,1977),would only have clInicalutility ifpetients scored above the cut-ol1,whiledismissal 01a dementingprocess couldnotbedoneIIa patientscored withinme normalrange.

1.1.2.Coolldg ."l lgorithm

Cool idgeand hiscolleagues (1985)proposeda more recentWAIS based algorithm to distinguIsh organic trom nonorglnlc lIIneu. TheyslatlslJcallyanalyzed dataITom In earlystudy (Crookes,1974)Inwhich148 patientswith unc8n. lndiagnoses (dementiave.dapression) were te:ltad withtheWAIS and classilledalteratlees\ oneyearIollow· up es eilher dementlngor I1epressed.The Crookes studyfound thst dementlng lOubjects scoredbeet onthe Vocabulary sublestand worstonBlock Designand DigilSymbol.Coolidgeendhiscolleagues (1985)re- analyzed the dala!rOmthe

ceceee

sttJdy'::Idloundthat theVoc abulary eubtest was the/Slly onewhic h did!!2!discriminate between demantlngand depressed individuals whlletheBlock Designeubteet discriminatedthebest TheyIllen deriveda WAISalgorithm:dementiais

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indicatedHtheVocabularysubtest ag.xaled SCOI9 Is greater than or equal totwk:eh Block Design subtut ag.xaled SCOte

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281.0• dementie),and appliedtheelgorittlmtothe data fromthe ClOOkea study. They found that this algorithm correctly classified neefly 3/4 of dementlng (74%) and deprlm8d (74.5%)Incllvlduals.However,theauthors didnotadequately report what dl89nostlccriteriawere used to assign the follow·upclassifica"onsof"dem8ntla'or 'deprasslon',leavingthevaUdl1yend rellabl!lIyofdiagnosesin questJon.

A lalerstudyInvestigated the 8CCI.lracy of the same algorllhmf'J.:::2BI.D) In dlstlngulshlng OATfrom normal elderlycontrols, elderlydepressedIndividuals, and ollter organic conditions (I.e.,MID,Huntington'sDisease,KorsakotrsPsychosis,and Alcoholic Demende, Crawford, Parker,Besson,& eeeveo, unpublishedmanuscript).The authorsf~ndthatnone of the normal eldefly subjectsand only19%of tooelderlydeprossedpatientsexhibitedthisprofile. ThiswasIn contrastto680/0 ofOAT pallentswhoexhibitedthe profile,yielding a classification 80curacyof 84.1%when OAT was compared withnormal elderlycontrols.and 74% classification accuracy when OATwes comparedwith elderlydepressedindividuals. Further,a comparisonof OAT wllh each 01theother organic conditions,indicatedthat thealgorithmwas benelicial lndistinguishing OAT frorll Korsekolfs Psychosis(classification8CC\Jracy• 78%), AlcohOlic Dementia (clasallicatlonaccuracy· 85%),and Huntington'sDisease(classification accuracy· 75%), but less benellclal IndistinguIshingOAT from MID(classifiCiatlon accuracy- 64%).In other words, the algorilhm Will beneficialIn dlfferenllal dlagnosls.:l fOAT fromnoma!elderly COfItrols, elderly Depressives,Korsakoff'sPsychosis,AlcoholicDementia,and Huntington'SDisease.It wasla18 sUOC&5.!Iru1ln differentialdla9"0$ls of OAT from MID. However,theeuthore'eeparanon01thasa two types of dementIa (OAT and MID),indlcaled thatthe algorithm(V.::281.0.)was probably more beneficialIn dlsflngulshlngOAT from Normalsand Depressivesthan In disUngulshlngMID from Normals and Depressives, however this was not statisticallyInvestigated. thereere, althoughthe algorithmmay be relatively aJOCBssful inthedifferentialdiagnosisof OAT,)t maynot be81 st.lOCflssftJllndifferentialdfagnosi!\01patientssufferingfromthe MIDlorm of dementia.

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1.1.3.Y.PSpIl1

A commonly used IndexforIdentifying organicity in clinical practiceIs the WAIS,wAIS·R v·pSpilt The V·P Split la determined by subtractingIhe tolal PIC scorefromthe lotal via llCOf8 {Flelcl,1960).The logiclorIhla WAISfNAIS·R based algorllhmIs the same as used In the other WAISfoNAIS·Rbased algorllhms menlionedabove. Thai Is, PIaIs considered 10 containmo...

"no hold' tasks (i.e.•lasks which requiremore cognitiveslrategyand partiCular types 01tasks, such asvisuaf.spallal tasks, which appear 10bemoresensitiveto organicimpairment), IhanVIC.

The commonrule-of·lhumbIs that IIthediscrepancy15 greater een or equalto 15. thereIs strong needlotfurtherInvestlgallon (Wechsler,1981, p.36).

AlthoughthisequatKmI,commonlyusedIn clinicalpractice, Ilttlaresearchhasbeen carriedouttodetermine115validity.Further,much01the researchthai has been carried outhas disreg ardedthedirection of me discrepancy(Field,1960;Grossman,1983; Nagllerl, 1982;

Wechsler,1981).Thatis, discrepa nciesnevecontained bothVIC"PIC and PIC"VIC added together.even Ihoughthepredicted directionlor determiningwhetheranindividual 15demenllng clearly15 VIa"PIC. Clinicaluse01 lrequencytables generatedin the ebove stuclles• deterrrrloeabnormalityofobservedV·P Spllts,leads 10 potentiallyInaccurate judgements 01!he presence 01cognitiveImf.~:rment,due 10thounproven assumptionmet Pia" via occurs equally frequenlly asVia " PlQInthe cognltlve lylntact generalpopul&lion.Further,evan with the methodologicalIIaw of combiningbothVia"PIOandPIC" via . Field(1960)foundthatI di3crepancy 01150rmore polnt' betWeenVlQ end Pia (VIQ"PIO) occurred in alleast10%of his sampleove r age 65.suggesll ng thai a 15 pofnldiscrepancyIsnotII.clesr Indicator 01 cognitiveimpairmentInthe elderly.This IsIn contrast to the three otherstudies(Grossman.

1983;Nagl1eri,1982; and Wechsler,198 1),eUusing theWAIS·Rstandardlzall oosample~• 1880), which Indicatedthai a 15 polnlpredicted dlscrepancy(te .•VIQ greaterthan or equalto1S pointshigherthan Pl0) occurredrarely«1%)inthe non-Impairedelderty populationand there fore was suggestive of cognitivedeflcns.However.itwas unclear whetherField's (1960) sample wasrepresentative01the generalelderlypopulallonor whelhersubjects were screened lor oognnlveImpairment. Therefore,meee 'equivOCal"resultscouldeesilybeexplainedIIField assessed a geMral elderlypopulallon,and the otherresearchers8$.98ssed e screened population.ThatIs, ifReid's sampleIncluded a generalelderlypopulalinn. ItIs likelythat 1IOlT1e

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demen~ngindividUalswould havebeenIncluded ,Ihus potentJallyInllatJng the observedV·P Spilt (VIQ..PIC),Incomparison with thealze01 the y.pSplit01 thenon·lmpalredelderly subjects comprisingtheWAIS·Rsampleer:"I PIoy~byGrossman(1983),Nagllerl(1982),and Wechslar (198 1).

Onepair01re5ellrchef3has preeentedseparateVIa"Pia and PtQ::.VIa norms,using me non·lmpalredsUbjects comprising Ihe WAIS·R standardisationsample (Matarazzo& Herman, 1985).Theyfoundthat8.7%01allsubjects'VIO swere 15 ormors pointsgrealerthantheir PICs (8.5% aged 45-74),and similar figures werereported lor PIO::.vIa. This meansthat approximately9}1oonon·lmpalredindividualswouldbesuspected10beImpeiredbyIhe 15· poInt rule-of-tnumb regarding tha V·PSptft.This figure does not even reachIhe oommonly accepted slatlsllcals~n ific.nceof 5%,leialone addressthoIssueof clinicalsignificance.

Aeseerch Inve:ltlgatlng whether or not demenling Individuals differfromnondemenllng IndividualsIn the sizeofthoverbel performance discrepancyIndicates that the y.pSplit Isnol a highly promIsingIr:dicator01 deme nlia . Hart, Smith.and Swash(1986) compered elderly dementlngIndividuals with elderly nondementl ngIndiv iduals on various cognitivemeasures.The authof3 roundthattheWAISy. pSplitwas not 01 greatenough magnltlJdeto bea sensitive Indicator01intellectual decline,In theirstudy,somedementlng Indr.oiduals actuallySCOfedhig her on PIO

rna

^hold1than on VIC(~hOld1,and enrene discrepancies Infavou r 01theVIO (i.e.•up to 21·25paints)ware roundInbothdementlngand controlwbjects,

lazak (1983) weecr~1c81of lheV·PSpilton two accounts. First,shaarguedthatviaand PIO arebOthcompilations 01functions whichaF'l'dIssimilartoeach otherand haverelatr.oelylow IntercorrelatlollS.Second,she notedthatVIC and Pia overlapIn!unctionsmeasured. She attrlbuled theovariaptothe method which was used to assignsubtes\stoYIC and Pia (dictated ralher than esslgnedthrough teeteranalysis). Further,ilhas beenreport ed that many other conditions (e.g"psychosis) mayproduceViQ"PIC, reducing !hIs measure'sspecificityIn identIfying demerllla(GUeltln. ladd, Frank.RabIn.& Hiester.1966).

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1.1.4.SubtN 1 scatter

Anotheroommonlyused bul3CaR:e1yresearched clnical·ind~.~or demenl:1a.IsWAiS OfWAI5-RSUblUlitC.Iner (leZlk.1983).The~frequentlyused method ordetermining sublest3Ca!!"IsdeY\lltlonabetweenpairsofaublnts (FI8Id,1960).RnrntchtodeI:&rmiMthe extent01subresl: seatterInthenon-lmp8l redgeneralpopuIatlonha!!k'ld ica ledthat • IhrM point dblcrepancybetweenanytwoSlJbl:aSl!!OCCUr!linlesslhan1~ofnonnaDylunctlooingindividuals (lN8ChsIer,1981.p.36).OtherresearchhasIndicated lhat !Caner013.S+4.3scaled scores ooc:'.JrsIn5%ofthenomIalpopulationandscatterof4.6-5.5scaled3COr9SoocursIn1%01the normal population(FI8Id,1960). Further,some WAIS·RSlJbtllm(Oigit Spanand Object Assembly)exhibit more variabilitythan others (Vocabularyancl lnrormation) (l ezak, 1983).In oll'lerwords,Itteremay bemorevariabilityinth6non~gnltlvelyImpairedpublic:than oogJnally assumedandtherefore cUnlelansshouldretrainfrom using subtest gestler as a maans In and01

!tsalffordia9nosing dementia.Furt her,muchofthe researchthaI hasbeencarried outon subtostscatterhasusuallyInvolved mentallyretarded individualsorchildren(e.g.,Coolldge, Rakoff,SChwelenbach,Bracken,&Walker,1986: Aoszk owskt&Spreat,1982;1983),andhas typicaftyrevealedthatsubtestecenerisrelativelycommonInmentallyretardedIndividuals (CoolidgeataL,1986)andlowerfunctioningindividualsin g_ral(ROSZkowski&Sprea!"1982).

Therefore,SUbt8S1!lC8nerdoesnocappear10bespeci!ictoclementiaandItsuselorcliagl'lOSling exga.nc itymayInaccuratelyidentifylowerfunctioning Indiv idualsISc;:ognltivelyImpair ed.

1.1.5.Summery01WAiSAlgorit hms.

hIsevident !romtheabovedlxusslonthatnu;hresean::h hasbeen carr1edoutinsea~h lorthebestconfigurationorWAISor WA I5-Rsubl:eststhatd~ inguishcognitlvetyintactfn.m cognltlvely nonint actsubjects. Although~configurationshavebeenmoresuocessfulthan others,nonehas proven satlslactory In thedetec:tlonof dementlll (withthe possibleeKceplion01 Cool idgelindhiscolleagues'.1965.form ula which requiresmoreresearchbefore clinicianscan usethe algorithmwithconfldance). AsMiller(1977,p.109)putit,'For a lewpsycholo~ islsthe Marchfor theright Wechsle rsub·testcombinationstillgoes on rather like themedieval alchemist'ssearchlorthephilosopher'sstone,and withaslill l.likelihood01ultimate success'.

OneeKPlanationfor thelack01success 01 thesepurporteddel eriorli Jon Indices,isthattha

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10

WAIS/WAIS-R"hold"

v.,.,.

'1'10tIoId"FormulaelTW.yi~tubteatswhlr.:hare not1tIebest Indlc.lt0r5ofcogntive- 'yandINIftenance.ForInalanee,asmertIoned~sly.one grou p01~,..ra.r, ~cMdfrom•IDIIowupstudy,that1MYocabulal)'tub"'''orttle WAfS wasttle~subtestwhichdid!!!!!dlrrerentl.tlllb8tweeneld«1y~andeieler1yGepresaed JndtvlduablCoolk!geeI...1985).~,_ _II researetln have nocldthatMUroIoglcal1y mpal A!JdInlIlviduabshowsomedecrements on

!!

WAISor WAIS-Rsubtests(lezat, 1963;

Rus.MI~1972;Vogt& HHton. 1971).

1.2.Measures ofpremorbld Inteili gent;t!

Severalmethods or estimatingpremorbiclcognitivefunctioningQ.e.,theidstlmaledleYeiof Intelligence priortothe dS'Ielopmentof 8 dementlng dlsonler) havebeenproposec'.These lncluda the useofdemographicInformalion,theVocabularysuble, !or theWAISor WAIS-R,and wordreadingabilltlp. ThenlHI n::honthese IndicesIlll'efallyindi;atu theyhaveenjoyed benerSUCC1I~tl\8nthe WAISfN AIS·Ralgorithms discussed above.Theyarereviewed belowIn termsof lheir development.$UCCetSIn correctclassificationof demenllngindividuals,andtheir 5IJCC8SSIncompatbonwilh1lI8Chothet.

One COl11IllCM'ty usedmethod orestimatiT\Ipremortlidn..~Isclnicalguessworll basedon demographiCInlonnatlon.ThelogiCisthaiIntelligencelevelshould be relatedto sud!

.,IOITTllt01 asedl.catlon.-lCloccupation (OChet (.I8l'I109"lphcIr1lofml tlon hisalsobeenusedat dl3cu~beIow).However.thisc.nleadtolargembef,lcJlallcm withtheelclertyduetooften scanty educallonrecordsandImlled early 09poftUn/liIlSleadingto~donsbelowtheir capablitllll. Funner.manyeldarlyfemaleshl~eneverbeen gelnfullyemployedandmmatas h.~abeanbasedonthecnJdemIll3Ure01husbsnd'soccupatlon.

Nevenheless. some recentwork has beencarriedoutIn theUnited Stales, theUnited Kingdom,and CanadaIn wllleh demographk: informationhIS beenenteredintoregression equallons toyielclaslin ated premorbldPerformance. Varb81lndFullSealeWAISfyVAIS-A IQ equivalents (Blrona.Reynolds,&Chas lain.1984;Blair&Sp~n,1989;Crawford,Stewllt, Cochrane,Foulds.Basson.&Park....1969;Ep~ger,Craig,Adams&PIDOnS.1987; Karzma/k,

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11

Heaton, Gram &. ManheWs, 1985; Wil3on, A03fJnbaum.Brown,Rourkf\ Whitman,&.GrlHlI..

1978).Thepioneeringworlt InIh~allla was carrlecloutbyWilson and his colleagues (1978), whoused most of1M WArS alan<fardlz8t1on sample~-1100)to develop demographic equations10predictWAfS 10.They buill regressionequatlons which contained InloRnlllon about age,sex, race, education,and occupationwhich predicted54%ofthevarianceIn WAIS FSIO, 53%In WA1S VIC, and 42% in WAfS PlQ.A furtherstUdyusing140 nt'Urologlcalpatlellts versus 140 non.neurologk:al patients,comparedtheefficacy of these d8l'Tlogrephicequationswith the elficacy01the reVIsed Wechsler DO In clasailylngcase9 within thetwogroups (\NIlson, Rosenbaum & Brown,1979).T•.)yfound thatIn boththe Initialrun and the doublecross veueeucn run,the demographicequationswetesuperiortothe revisedWechsleroa (71.80/0VS.

63.2%Ind 72.8% vs 61.8%correct classi!lcallon01cases,respectively).The WIlsonequations were crOS3 validatedbyonegroup using a large 3ampla

lli ..

491) of subjectswitllout neurologicalproblems (Karzmark etet,1985).Karzmark and his colleagues (1965) compared WAIS obtaInedscores withtha predicted scores usingme Wilson demographicfonnulaa.TM)' found that demographicvarlablas predictedleu ofthavariance In WAIS FSIQ Intheir,ample Ihan IntheoriginalWilson study,Thatis,only46%01tno FSIOvariance was llIX:Ounled forby Ihe W(lson formulae fortheir amployedsubj&cts andthe amount dropped to 42%

w'-

considarlngthe total sample,In comparisonto 54%In the Wilsonetet,(1979) study.Thismight be explained,howover,given thai the Wilson formulaewere developed using 8 sample lrom 1955. II wouldbeo.(pectedthattha relationship between demographic v.rlables and IQwould change OV6f the so ya8f3 between tne Kerzmark et al.(1985) study and collection oftheWAIS standarcllzatlon sample (Wechslar, 1955).

Barona crealed similar formulae for estimation01WAIS·R10scores (Baroneelat,1984).

UsingtheWAIS·R S1andarcllzallonsample

lli ..

1880). demographicesllmated pramortlld10 equalJons were determinedbyregres9lng the Wilson demographic variables (I.e.,ege,sex,race, education,and occupation) plus two new demographicvariable s(urban vs Nral residance and handedness).against WAIS·A FSIQ.VIO . and PIO.The Barona damographic equationshad.

lower predictive accuracy than tha Wilson equations. predicting only36%of the varianoa In WAIS·AFSIC, 38%In WAIS·R vIa and 24%in WAIS·RPIC. The equationsware cross- val id ated on a group 01 80 neurologically normal subjeCt'. and aocuracyof the demographic

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12

equatiOnsIn distinguishingbetweena group0183 brain impairedSUbjectsandItlen...roIolllc.Uy nonnal controls was detemllned (EPPlnge1'etat,1987).Cross-validationproduc:eda substam....

Il'lCtftseIn ptedlctlva accuracyOV8 rtheBaronestudy, with!hedemogrlph lcequationsprtIdicllng 58%01thevarianceIn WAIS·R FSrQ,61% In WAI$·AVIC ,and36%InWAIS·R Pta (Eppjnger81 81..1987).Further,therewere noslgntficant differencesbetweenneurologicallyMlmel andbrain Impairedsubjects ondemcgraphically 831imated la, buttherewaresignificant differences betweengroupsonobtained10.However,although there werefarge significantdifferences between.~!m.ledandobtained10lor brainImpaired groups. therewere also signllicant differencesbetween estimated and obtained /0scores forcontrolsubjects,Indicating thaI the Barona demographicIndex(Baronaatat,1984)consistentlyoverestlmatedla,

Barona andChastain(1986) attemptedto developmoreeccuretedemographic equations topredict WAIS·i'10.TMyre-analyzedthedalafromthe WAIS·Rstaooatdlzationsample, exckJdlngthefirsttwo age cetegories (16-17years and 18·19years),sincethesesubjects' occupationalcocIinglwere primarilybasedontheheadof household'soccupation,and excludlng racesottl er than Black orWhite,sincethere wereverysmall numbers inthe 'other'caf8gOfy.

The re·analysll onlt1esmaller sample

tt! •

1433),produceddemograpi~·cequat ions which predlcted morevarianceInWAIS·A FSIO,VIaandPia thantheInitialBarona al ai.(1984)study (43% ve.36%,47%VI.380/0,and 28%VI.24%,respectively).ThaseresultlIndica tethattn.

revisedeafClllaand Chastain (1986) equations shoUldbefavouredoverthe origin al equations (alronaet at ,1984), when predlctlngpremorbld 10 forBlackorWhile plllen!s ove rthea~01 nineteen.

Similarequallonshavebeen developedintheU.K.toestimate premorbid WA ISIQ from demographicInlonnaflon(Crawlord, Stewart, Cochrane,Foulds,Besson, &Parker,1989).

Crawford and his colleagues (1989b)found thet ademographlcequationconsistingofsocial class,aee, education,andsex,predicted50%01the variance inWAISFSIO andVIa ,and300/0 of the variance In WAISPiO.Therelearchel'3concludedthat demographicequationsmayhave some utility InpredictlngpremorbldIntelligence.

Thesedatasuggastsome promiseIn the use01demographicvariables to astlmate premorbidcognitivefunctioning,however,someproblemshavebeendescribedIn theliterature

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(Eppinileretat,1987;Silverilein,1987). These InckJde the restricted range of predicted10 using Barone ancl his colleagues'(1984) equations (89-120),!he dlfftcufty of IIttlng many occupations Into tile aarona claasiftcation eystem,the lack 01 finely-tuneddlacrirnlnatlofla betweenhigher education, and thelack of control forIndivi duals who are high or low eel-devers (Eppi nger et at.1987).These problems might Int8f1SityWhile using the equations wllh an eldally population.With this speci alized group there may nO!beenough varietlonIntype01 occupation or amount 01 educationtobedi9CriminatoIY,dueto reduced lileopportunities. Further.one researcher found !hat neither the Wilson northe Barona demographicfolTTlulaewere accurateIn class ifying patlentsInthe seven Wechsler10categories f'Jery Superior ,Superior,HighAverage, Average,LowAverage, Borderline ,and MentallyRetarded,Silverstein,1987). Eventn. best estim ato!sln Silverstein's(1987) study[l.e.,Wilsonequations)mlsclass llie<lmore than hall altha subjec ts(I.e.,placed !hemIna catagoryabove or belowwhat Ihey should havebeenIn). In addition,Wilso nandhis colleagues (1978) themselves pointed outthat theirpredlcted premor'old demogra phic equatloosbased on subjects !rom 1955 would overestimatel Q due to the increased educationalattainmentofIndividuals slnca meo.Thaoverestimation 01 fabythe Wilsonformulae wassubstantiatedIn astudy comparing the WAIS,dem09raphlcestimatesusingWilson's fonnula!,and another test ollnlelligence(theQuickTest)Ina sample of50patients with mixed pSyChiat ricdiagnoses (Lew,Price, & Herbert,1981).Theyfoundthatthe Wilson equations lor estimatingpremorbklla slgnilican tlyoverestimatedWAISla by an average 017.610points .

Funher evidancelotthe Wilsonatal.(1978) formu lae overestimating10wasfoundIn II study comparingneurologicallyint act psychiatricInpatient s withpsychiatricoutpatients (Klesges, Sanchez,&Stanton,1981),and has also been 1000ndIn aeenee of studies (Bolter,Gouvler.

Vene k rasen&Long,198.2;Gouvier, BOlter,Venek lasen&Long,1983; Klesge3,Flshe" Vasey&

Pooley,1985)investigating the utilityof his equations In differentiatingbraininjured from ·pseudo neuro l09lcal" patientsQ.8.,patients who were referredlor naurological testingresultlngin normel test results). In ganeral,these studiesfoundthat theWilsonelat (1918) demographic10 ostimates(estimaled WAIS FSla,via and Pia) overest imated premor bid IQ,therefore risking a greate, possibility01mlsclasslfylngnon braindamaged patientsas braindamaged as a result of the dlscrapancy anafysls(La.,a high premorbldmeasureis takenas evidenceof organicity). In add lt io n,the groups ofresearchers investigated theutil ity 01incorporatingWilsonat 81.'S(1978)

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t.

SllQliIntedMlucatloneladjJttment(ecucalion al.,.;g1'Qx0.82).to~lIeCttheincrH.In educanonaJartlitlrNnltlnce 1955.wtwlWaon

..:11.'.

<19781utJ'plewascohcted.AIofthe ... stlIdiM(wllhh exc.plbn01the cognitivelyunmpairedpsydIlatl1coutplltlentsirI'<In ge.

et ....1981).IoundtheM4d~tI:lUf'ledInIitttetono inproYementInpreddiveKCUr.cy ofthedflfl'lOgflphlcequations"andInsomecases actuarydeere_. . . . .predictiveeClCVfltCy.

AllhoughKIng" tit11.(1981 )cautlouslrIpprovecltheclinicalute01eclucationally·ecI;"sted W1bon • at(1978)demogtlphic nlmllesofpremorbIcl10.theOChergroups otreMIImwrs mentionedaboVe (BollerIIIaL.1982;Gouvie retat ,1963;K~.s81aI.,1985).di3COUl'aged th8tl'usedueto questiOnablevalidity.

Theatlove studies (Bolter81ei, 1982;Gouv ~81 al.•1983;Klesgeset at,1981;1985) have been criticlz8ClbyCrawford (1989)on severalaceounlS.FIrst,III 0'the studies used Clinical subjects (I.e.,psychl. 1TIcpauenls or·pselldo n9IJfologk:alpallenls·wilhno evidence 01organic deteriorationon.ICATscan). However,!ntollectuallmpalrmentInthese cl)nlcalsamplesIsrlkety.

Forexampte,negaUveCAT scenresultsdonO! rule out cognitive Imp.lrmanl. Funher,

~ophrenilartd/ofQ associated medications~k.JyIHOCIUC85Intellectual im~irm ent Ctlwford (1989)therefore atguedlhlt!hesesubjectswerenotaelequalecontrob,abenercontrol samp lebeingcognitfotelyunmplireclsubjects.Indeed.Ctawbrd(1989)poWltedout thatthe control:subjectsusedInKlesges litIt(1981,psychlatricoutpe.!ldnts).andKlr.lges etIt(1985.

"pMUdo neurologiCal'" pat*U)hadbwet'meanIQ tICO/tlStl'W1wouldbeexpect edin"

c:ognitlVelyrtact:USumple{1.5IndO.SS.D.lower,Nspecti'VeIy).

Intellectulllimpalrmnin thecomparativetamplewould di!ltol'l.r&!lean:tl finding sIntwo ways. Fnt,therewouldbeweaker c.orrelallonsbetweencIernograph icailypredictedarid observedIQ.andsecondtl'ledemographicvari a bllts woulcllppearlOOYere stiml lepremorbidIQ Incompari son10obtained 10.These ware preciselythelirocllngsallheabov l stuelies(Bolteret 11.,1982;GOlIY.ref111.•1983; KII'geS II el.,1981;1985).

Crlwford(1989)oUlllned two 1I.llt her met hodological"aw8 In Ins loovastudi e s(Boltaret aI.,1982: Gouvlarali t,1983;KIeSQas al aI.,1981;1985),whichla8vas IhelrconclusionsIn qua stlon. First,thelu11'lor1neglectedto emuA!lth ettherarlge01 demoqraphlC variables occurringIn theirsamplesA!lllectedIhe range04 the sevaria blesIntheganer,, 1 popula tio n.

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11

Therefore ItIspossible tI1al spuriously row estmates ofthepopulation oomtIation between predictedand observedIQ were obtained.Second,two ofthe studies(Bolterlit81.,1982 and Gouvktret III.,1983)used small sample sizes (23 -PMlUdo n.... roIogical· pat'-nta, 11 recovered and1tnon-recovered brainInjured patients). Use of multiplepredictor variables, such as demogl1lphic variables,wiltl smallsamples eln produce misleading high orlowcorrelationsby chance(Crawford,1989). Inlight otthe abovemelhodologlcelproblems,Crawford(1989)argued that lhe conclusionsreponedbyKlasgnet81.(1981; 1985),Boller at at (1982) and Gouvleret al.(1983),thatJs,ltlst demographic variablesoverestimated10 andpredicted.small amountof VBri8~In WArS IC, wereunwarra nted.

A further concern regarding the use of demographic equations to predict premorbld intelligenceis thattheycan onlybeu3edlotpredicting Intelligence 01 inclNidualawllhsimilar characteristics u the st and,",rdlzatlon samples. ForInstance. the relationshipbetween demographic variables and IQ may notbeequivalentbetween countries (Craw lord,Stewart, Parker,Besson,&Cochrane,1989).Thatis, peoplemay requiregrellter inteiligente in one country 10 attain a similar educationlevel In another.Inotherwords,applying the currently IIveUableequatloos10 a sample IToma different country mightnotyield an accurateprlldlctlon 01 premorbld Intelligence,end therefore unique equations shouldbedevelopedtor eachunique poputetlonstudied.

In defence 01thedemographic method 01 predicting10, however,Crawford and his coneagues (1989b) pointedout that predictionotpremorbl d fUnctlonl1l9bydemographic equetlons hasthe graet advantage of baingcomp~tetyindependent 01 currentcognitive fUnctioning. Funher,in comparison with the use of word readingabilities (e.g.,the NART) 10 estimate premorilldla,demogrllphlc equations can be used withcertainpatients(e.g..dyslexics and Illilere,es) withwhichtheNART cannotbeused with(Crawlord,1989).

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11

1.2.2. WAIS/WAIS-R VocabUlary.ubied

SorM rMelrchershIVe notedthattheVocabularysubtest oflheWAISjWAIS-RIs the least

"dementla·sensltlve-(1.•••I..sllikeJito sutler perfomlance declineIntlamanllng Individuals)01all fheWAISM'AIS·Asubtette(Cool'dgeetat,1985:Lezlk,1983).Further,Coolidge and his coll••gulls (1985)foundittobethe~WAIS subtestthat did~di!ICrimlnate groups (dernenting ve.control subjects). ThaiIs, althoUghneittler theVocabulary subleSlnor any other cognitivetest IsIlk_tytobecompletely "dementia·lnsensitive",It hasbeenobservedthai demanllngsubjects performbene,onitthanon anyotherWAIS/WAIS·R subtest. In addition.the Vocllbutarysubla, l has beenreportedtocOlT1llatl Ihe highest wnhboththe WArS and!heWAIS·

A FSIQ In comparisontothe-::;ldfWechsler eubteets, lhecorrelatlonsrangingbetween0.85-0.87 (Wed'lSler.1955;1981).Therefore,theVocabulary sublas!appearstohIVesatisfiedsome 01the criterla necessarytobeused as a premorbld10indicator namaly, thatitCOO'elates highlywith WAISN/AIS·RFSIO and thaiitappears todiscriminatetheleest between dementlng and nondementlng Indivlduels,incomparisonwith lhe otherWAISN/ AIS-RStlbtesls. However,In a review article, Crawford(1989) reportedthaIs8Veru! studies(Russell, 1972;Swlercinsky&

Warnock,19n,cited InCrawlord, 1989;Vogt & Healon,1977),have roundIhalnoncognitivel)' Impaired Individuals performed significantlyhigherontheVocabulary sublesl thanoognitively impaired individuals. Crawford (1989) cautioned agalnsl readyacceptanceorthese results, however, since the researcher31 didnotlake eithereducalionaldirlerencos (AU388I1,1972;Vogi&

Heaton,19n), or premornldintelligence diflerenoes(SwlelClnsky&Warnock,19n, ciled In Cr~wlord,1989) Detweenttle groupsinto consideration.Therefore, ills Impossible to discern whetherperformancevariabilitywas duetopoorer(e.g.,educational)backgroundsofthe cognilivelyimpairedgroup,s 'alre,Ihan cognitlvely ImpairedsubJElCIS'reduced ability10 perform well onthe Vocabula!ysubtest.

Nelson andMcKenna (1975)propo!l&da methodlor estimatingapremorbkl lQ score from theVocabulary subtesta lone.By regreaslngcontrol subjects'scoreson lheVocabulary sublnl against their scores onthe WAIS FSIQ. VIQ andPlO,they createdregressIonequationsinto which Vocabularysubtsslage.scaled scoresof Individuals couldbeenlered10producepredicled premortlldWAIS 10 scores. TheseVocabtJlary las couldthenbecomparedwithlhe currentIQ measures ofWAiS FSIC,VIC andPia InneurologicallyImpairedIndividuals,todetermll19the

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17

axt. .of!hedl!CNptlncy~"npnldlctedanctobIained 10.andcllnic.llt'fthiImethodlipbeen u:Mldto.-mat a1Mdeg ree or cognlllvadeterioration. Published SlUdles on 1Mpntdicted VocabularyIQh.~prIrnatftyappelrMfInthe eotten01COtnpill'lngIwthestimatedlQInorbd lOsdelermlnedbywordre-.:ling1estt,andwitheftltorebedilC:l.Medbelowunder the heading of2.4.3 .NARTincomeatbonwllhoItIermethods01distinqul Sh'ngdemendnqtomnondementlnq

~

1.2.3.Word ... adlo-,gabr;lty:TheSchone"G.-.dedWord ...Milng Tnt

Onepairof rfl:Mlarchtnnotedthroug h clinicalobsaNation!hitreading ability(8OCUracy01 oral pronunciatio n)was relativelywell·preS8fVedIndementlngIndividuals (Nelson&McKer..il, 197 5).AJrther,they reasonedthatsincer••dlngof complex senlences",quires useofsyn tax and semanticsand the reforeIsmorecognltlvelydem andingthanreading singu larwords, the latt er wouldbedeemedmorau!lEtfulIn8stlmal lr.gpre -i!lxJstlnglnlellectul l llJncUoning(Nelson"

McKenna,197 5).ResearchInto the usel\Jlnessofwordreadin g

IS.

^valid^estimator01premorbid Intellectuallunctlonlng began with the&:honeAGraded WordRead ingTest ISGWRl).

constructeclforU~withchlldJeofrommostelementarylevels(Nelson&McKenna.1975).The authors admin ist eredtheSGWRTandtheWAiS1098neurologicallyInt.etsubjects lonegroup01 hospitlllizecland0.0-.groupofnonhospitaliZedoontlOls)NId45hospitaliZeddtln'IentInGsub jects.

FlI1dings!romthisstudysupported thehypothesislhalwordreadingabilItYandgen eral intelligencewentpositivelyc:orreIaledInnormaladults

l!:•

0.75•.2<.001.!•0.78,.2 <.00 1. !• 0.58.

e

<.001betwMnreadtIgiIOOf1IandWAISFSIQ.WAJSVIC,andW....1SPIC.respective~).

Furthe r.therewete00 a1gnilicantdlflerwces betweend9mentlngIlI'lclcontrolgroups onru d ing ability(SGWRTscores),butmerewere signilk:antdifference:lbetweenthe twogroups onall measum01 theWAIS.ThIsledtheauthorstoconcludethatalthOugh readingabilityb Iik-'Y atrec:tedbyseverityofdementia, IIcanbemaln1alneclalahighleveldespite deterlorallonIn olt'l., ,kills. RuddleandBradshaw(1982) replic atedNelsonand McKanna's(1975)study using 78 noona'controls ,75 pat ientssuspectedof cognklve impairment I10tdue10 • damentlng dlsof9t (dividedInto confirm edcorticalatrophyandequivoc alcases) .and22 damonting SUbjects.Thay regressedtheSGWAT againstWAISFSIC.vtaand

Pi a

In theircontrolsubjact3andfoundno slgnlflcanl difl'e renoa between N,t1sonandMcKenna'sequatio nslorpredictingWAIS FSIQfrom lheSGWArandIht..own.I~a~JtIon,lheyfoundIhala_01thepatientgroupshad signiticanlly

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11

h1gner meandl9cl'1tpancy!ICOreSthan the control subjects (calcul.ll!ldby SGWRT~Id mlrl.l. obMrvedWAS to).butthe dementlnggroupdlspa.)4dthehighestmean dlsc:r.parcy eoores.The alJthorwcorctud-'thlll(I)SGWRTprovided...lIble.stmalaofven-a1 r.tellgel'lOlt,(b)theNOjIresslonequatlonlorpred"1CtingWAJS FSIObySGWRTproposedby Nebon andMcKenNIwa.8OCUnI1eandusefultocli'llca lpr~.and (elthat~01d~ ncy scores betweenSGWRT predicted WAISIQand currentWAlSIQwouldpfOlAJcelewer labe negativesInthediagnosis 01 dememlfl thanInthed~nosls01Ie"welld;.~neurological impaIrment.

Alt houghtnt!above mentionedstudies in dicatedsomepromiselortheuse 01the SGWRT Indl.gno~Jtlgdemenlla.criticismsagainstusing1tl1~measurlIncludedItslow10 ceilingol115, and thatthe lealIncludedImixture01reglJlarandlrreg ul.rwords, many 01which wart long (Nelson&O'Conne ll,1978).Neloonand O'Connell(1978)foundIMI dem'itntlngindividuals made significantly mora errors thannormalcontrol'Inreadinglong regular words.The authors conclud edthtitthis was duetotheabilityof controlsubjeclltocorrectly guessthepronuncIation ofthewonls byapplying intelligentguesswork,alasltWhich was dlfllcult lorthedementing subtects.ThatIs,even lhoUgha neurologiCalryintactperson hasne\l1N'seenawOf'Clbelote ,if regular grlll'llT\aticall\Jles areapplied,thewordcanbepronounced oort8Ctly,Whiledem.ntlng individ u als Ireless~kelytoguessthecorred prorIJrciation.

1.2.4.Alessdem, ntl. un,ttlvewordreadingtest?:Th'NaUon••AduttReeding Tes'

TheNationalAdu ltReadingTest (NAAl)was develoPedIn111attempttoproduceII measurewhichwasterattveryunaffectedbythedementlngprocess,and10IncreasetheIQceUlng thattheSGWRToffered(Ne!*K1,1982). Nelson(1982)reasonedthatabetterestimate01 premorbld10would Involvea measure which minimizedcognitivestrategy 81thetimeof testing.

The NARTattempls 10dojualthIsbysimplyhavingtheIndividualreadalistof 50 shOflI"89Urar words (e.g.,gauche), andaccuracy of pronunciationIsscored. Shortwordsareeasierthanlong wordslorder.lentingIr.dlvlduala(0praceaaandthe irregularitydemandspreviousfamiliaritywith both pl"ORlnclatlonand spellingInordertoproduceacorreccresponse.Inotherwarda, Slbjectl are unable10usestandardgranmaticalrules tosuoeesslullypronounceIheword.

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11

1.2.4.1.P.~JopropwtI-=n.labHl!.y

TheNARThasreceived considerable support fromstudle.e.ttemptingtoesl:abliShIts reliability.The _ nu900dspl«·hart rellatluy,asdemonstratltdbytheSUlndanli zation sample (Chfonbech'sAlpha,,t-O.93.Nelaon,.1982),andanotherstudyinYestigatJ'lgHARTperform..-.ce or201neurologCallynormalsubjects (Spearman-&owntormJLI.["'0.90.Crawford,St8W1II'l Garthwllile .Parker,& Besson,1988).TheNARrslest·rete streliabllity oww8 1().dayperiodwas extremelyhigh(r..0.98)In 8 groupof 61MUroIoglcaJIynonnalsubjecb(Crawtlrd.Parte."

Stewart,BeS9Oft,&OeL.aoey,1989).Adequateinter-ralerreliabilitywas83tabUshedIn astudy comparing;0experienced ClinicalPsychologistNARTusers'Independentscoring ofthe NART lor 12 psyehology oulpatients'response••(Kendalracoefficient of cOI'ICOrdanca,yt-o.B8, O'Carroll,1967). This 8ffect was replicatedbyCrawfordand his colleagues (1989a), Inwhich5 experlenced and5InexperiencedNART users' sconngwascomparedon40NARTrecordings of noopatients.The correl_lionsbetween all pairs 01 experienced retereand between allrl teta togetherranglld !rom 0.96-0.98.h;:llOughthe ratersdifferedsignificantly Inthestrictness with whichthey scolWdtheHART.82%0.!tiewords had a90%Ofgreateragreement rete and 64%01 thewords hada95%Ofgrealeragreementrate.ThwitheNARThasbeenshownto beIr'llemalty consistent.tohavegoodtest·tetestreUabil~ .andtohavehighIrrte' -fat8f,.lIability.regardlessot whetherthescorer1$erperi8ncad or Inexperiencedwiththetesl

OfpatlWTlOUnimpottuc..psychometrlclnsuunenrsmuSInave COI1slnJctvalidity.Thatb. theyITIJSl:meuuretheconstNCtthattheypurport 10measure.Intheca!eofthoHART.itmusl be demonstraledthat meHARTmeasuresintelligencelevel.TheNARTwas standardizedon a group01120inpatientswith extrl..cerebral disorders,betweenmeages of20-70 yeaB (Nelson.

1982).SubjectJcompleted apl'OfaledWAIS(sevensutllests)andtheNART.and !romthisdata regressionequations weredev.lopedtoPl"edlctWAIS10 lromHARTerror scores.N.lson(1982) lound tha itheNARTpredk:led 55%01thevarianceInWAIS FSIO,60%In WAISVIO.and 32%In WAfS PIQ.TheNARTwas cro",.valldatedon alarger sampl.thanthestandardizationsample (I.e..

!i •

151 non-neurologic ally impairedSUbjects)withawideragerange (I.e.,ages18-88.

Crawfordetal.•1989a).Subjectswere administered th. NARTandtheentlr.WAIS.TheCl'O$S- validation slUdyrevealed Utatthe HARTIncraasad 1Mprf'lf!lcIedamount01varianceIniuDWAIS

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20

10measures u compared tothe S1andan;llzlIltion studyIn whichIIIprorated WAISwas uMd (66%

VS.55%InWAIS FSIC,72% YS.60%In W....IS VIC,and 33%YS.32%InWAISPta).Furtner, addition 01 quadralJcAnd cubic functions 01 the NART errorscore to the regreaslonmodelsdid not significantly Increase predicted to variance,Indic at ing thatthere were no ;.JOfor ceiling effectsIn the relationshipbetween NART and WAIS10 .Acombination ofthesl andl rdlzatlOfl samplewllh!toecross-validation sampleallowednew regression equationstobebuilt,which predicted 57%01thevariance In WAIS FSIO,63%in WAfSviaand 31% In WAISPia.Thes.

studiessuggestthat NART performanceIs a reasonablygoodpredictor of WAIS FSIOand WAIS Via,althoughItappearstobeless good at predicting WAISP1Q.

The NARTsability10 measurethe construct01Imelllgenee was further estabHsh&d In a study reveellng lnat tI1eNART loaded highly(.(J.85)on generellmallt.gence as meauuredbya principiaconponents enalysls In II group 01 neurologically r'IOnTlalsubjects who were adminlstared the fullWAIS and me NART(Crawford,Siewart,Cochrane,Parker,and Besson, 1989),Further,twostudies haveInvestigated theNAAT s correlationwiththeWAIS and the WA1S·R(Crawford, Allan, Besson,Cochrane, &Stewart, 1990,Crawford,Morrison, Jack, Cochrane, Allan,&Beason,1990), Inthefirst study,WAIS andWAIS·Aperformancewas comparedIn a U,K. matched samples design,inwhich100 pairsofneurologicallyintact subjects completed the NARTand eitherthe WAIS or the WAIS-R(Crawfordat al.,1990a). The NART correlated wellw~hboth ofthe current FSIQmeaauras~...0.78 withWAI~FSIO, ! "-0.72with WAIS·RFSIO). Theseoond study replicated tha designof the firsl ,Crawford et al" 19901::).

Fifty-lourmatched pairs of neurologically Intact subjects ware administeredtha NARTandenner lheWAIS orthe WAIS·A. TherasuRe were consistentwiththe firststudy, in that NART correlated highly withboththe WAIS FSIOC!...0.76)and the WAIS·R FSIQ

<r ..

.().79), Therefore theNARTappears tobeaval ~measure 01both WAIS and WAIS·A FSIQ in the U.K,

Work in CanadahasIndicated that the NART may also be avalid and reliablemeesure of Intell igencein NoethAmerica (Blairand Spreen, 1989).Theresearcher s created a Canadian revisedNART10overcome dtfflcultleswith regild 10vanationsIn pronunciation betweentheU.K.

and North America. They administered ahe origlna!NARTplus 54 new words along withthefull WAIS-Ato e samplaof 66U.S. and canedien neurolO(llcllllYintact subjects.They performed a series 01item analyses to determine the words which correlatedb83t with WAIS·R FSIO(words

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21

w!lh! !.0.2).They toundatotal or 61 wordswhich melthiscriterion. The ruvlsed WOldlist contained38ottheoriginalNART wordsplus23 new words.The fe5ellrchersFoundtherevised NARTtohavegoodreliabilityInterms 01a highInternal conslsfency (alpha -0.935),and'virtually perfect' inter-raterreUabifity<!: •0.99).Further therevisedNARTdemonstratedgoodvaUdity!, thall IKCountedfor560/0ofthevananceInWAIS·RFSIO.

A secondtypeofconstructvaliditymustbedemo nstratedforthe NART,namely.IIIthe NARTreJlIllvely "dementia- resistant"? severalgroups 01researchers have attemptedtoanswe r thisquestionbycomparingWAISand NARTpertomlances01neurologlcallyimpairedIndividuals w~hneurologicallynormalIndividuals.lithe NART trulywasreaieteottc theeffects 01dementia, thentheneurologlcallyImp aired individuals wouldperform equallywellascontrolsUbjects onthis last,Wh~8thayWOIJldperfOrmmorepoorly than controlsubjectsona measure 01 current intelligence(e.g.,WAlS/WAIS-A).

NelsonandO'Connell(1978 )found that patientswfthevidence of bilateral cortical atrophy received lowerscoreson allWAIS lasthanthe NARTstandardizationsample,yettherewas no slgnillcantdlllerenc1lbetweenthe groups onNARTperformance.Similarly,a groupIntheU.S.

foundthat20outpatients with mild-moderate OATperformed more poorly men 20 demographically-matehed normal elderly veunteereonmeasuresofepisodicmemoTYand conscioussearch ot semantic memory, yat therewereno significant differencesberweengroups on NAATperformanoe(Nebe!l,Martin,&Hom,1984). An Australian groupalsofoundthat Ulelr sample01 Alzheimer's patients didnotslgnlllc antfy differ from cognRivelyintact control sub;ects on NARTandSGWRTperformance, whereas theirdementlng sample performedsignilicantly more poorly then controlson the WechslerMemory SCale(Schlosser& lVison,1989).Rnally, In a studytodetermIneIn which conditionsof corticalatrophythe NAAT "held',cognitivelyInt!tOt control SUbjects' NART scoreswere comp ared withNART scores 01 subjectssufferingfrom differing types 01Intellectual decline (Crawlord,Parker,/:IiBesson,1988).SUb)ectswithDementia althaAlzhalmer'Slype (OAT),MultiInlarctDementia (MID),Alcoholic Dementla,end closedhead InjUry, receivedNARTscoreswhich didn01slgnllicanllydltferfrom demographically matched neurologically Int8C1 control subjects,but thosewithHuntington'sDiseaseand Korsakoff's Psychosis8COf'6CIsignificantly lowerthancontrols,indicatingthatthe NAAT Is arelatively 'dementla-reslstant'psychometrictestlormany, but not aUdisordersInvolving organicity.

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22

Onegroop01researchersemployed dl5Cl'lmlni ntfunctionanalysis todeterminewhether neurologiCalttimpairedindlVldull5wouldperformequally wellontheNART

a,

control subJects (Crawford . Hart, &Nelsoo,1990).Morespecific ally,they examined thehypothese ,that1.NART by~S8ltwould notdirectlydiscriminate group(Impaired ve.notImpaired)andthai2.NARTIn combinationwiththeWAIS wou ld imp rovetlagall cationaccUf&ey overtheWArSalone.TheIitsl series of discriminant functionanalysescompareda groupof32dementlngpatlen18with151

"healthy· controls,predictedNARTlasdeterminedbyCrawford, Stewart,Parl<er,Besson,and Cochrane's(1989)regressionequationsIncludingNART plus demographicvariable, . The secondseries01discriminant fl.mctionanalysescompared 40subjects withCATscanevidenceof conicalatrophy(predictedNARTlasdeterminedbyCrawford, Parker,Stewart,Besson,&

OeLacey's, 1989,regressionequalionsrorprediction01a shortlonn oftneWAIS) with the same 151 "healthy"controls(prtldicl ed NA AT lasdetenninedbyNelson&O'Connell's, 1978, regression equationsforereee ncnof a shonfomlof the WAIS).Theresearchersfoundthat althoughthe WAIS eceree correctly classifieda substantialpercentageof subjectsIn both sets of discriminant/unctionanalyses, In 5 out 016casestheNARTslgnilicantlyimproved classil'icatlon.

Further, asexpected, thebiserial correlation coefficientsbetween NARTest!mated10onItsown andgroup membershipwere nonsignificant,whilelhe biserialcorrelationcoefficients between groupm9mbershlpandWAIS10 measuresIncreasedinma9nltudewhenNART IQestimates wereperllalledoutThe researchersconcludedIhatNARTonIts owndidnotdiscriminate Ihe groups,wnereee NAATIncon)Jnctlonwith the WAISimproved discriminationbetweenImpaired andnon-impairecllnll lviduais over WAISbyitsell.

Anothermerl10d01 examiningatest's"dementla·lnsensitlvity'Is10delannine rowhich degreeIIcorralateswithdementiasevorily,That Is, IItheteslis relatively"dementia-resistant", onewouldexpectthat mildly and severelydementlng indiViduals wouldperformsimilarly on the index,O'Carroll andGilleard(1986)compared NAATandahair-lengthversionoftheMillHill VocabularySynonym'sScahillscores(MHVS, 8vocabulary testwith lewerdem andcharacteristics thanIhe Vocabulary suctestof theWAIS/iNAIS· Rj,In subjectswithvaryingdegrees ofeemeeue.

Theresearchers loond no significantcorrelation between measures01dementia severityandthe NARTortheMHVS.Further,Crawlordandhis colleagues(1988conlarenceabstract citedIn Crawford, 1989) found IhaltheMIniMemalStateExamination (MMSE),ameaWr801dementi.

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"

severity.'oWnsignillcentJyoorre/ateclwithNARTIn•sampleofPltlcmon' apal!ents.HoweII«, whentheI1IMM:hersdlvldtld their sempleIntoIhoseICOfIngabove.lndthose3COfingbelowthe d«nentIaClJt-otronItla MUSE.theyblnd!tieMMSE didnot significantly correlatewiththe NARTInthedementia aubgroup,bufdidsigl'lkat1tlyoomlla'.withlhe NARTInthenon- dementia subgn)l,lp.TheauthorSIm~adthiItomaan thattM"''''BEIs,.,sitlYatovariation Inpremortl ldto(I.e••not distr1butionffH).ralhllrthanthattheHARTIssigniricantlyoooeIated withdegree of dementi aseventy.

A further methodtorastabtiahlng valid ity 01a te3l suchastheNART,whichpurportstobe. stable,non-deterioratlngma.,ure01Inlellipence.Isthelongitudinal study.

"the

NARTIsIndeed I relatively"deme ntia-resistant"lest, then'891 scores 01Individualswilliprogresslvebrain deterioral lonshould notdecayeverlima.O'Carroll,Balkle,andWhlttick (1987)administered 8 dementIascale,Ihe NART,andah811·~nglhversion 01 the MHVS10 a sample01 dementlng Indivi duals and,a-admInisteredtheInventories ..year lalor.TheyfoundthaitheNARTwuthe onlylestwhiChdidnotalgnlllclnilydecUI'l8~!tk11lowup.

Despiteallthissupportive evlclercetor!heNART.therehalllb&ensomestudle!lwhich havenotfound.to"hold·a.wel l as atlglnally!lU99Wed(Bray".&Burdsan ,1990; HartItaL, 1966;Stebbins. Wbon.Galey,8emanf,&Foll.1967;Wood,Copeland.Fcnhaw.MuthJ. Abed.

Sharma,&Dewey,1984).Onegroup adm inislaredtheNART.theMHVS.andS8VlItl'aIindices designed10detectdementia.to.largerandomly'selectedcommurlrysample overthoIgIof65 (Woodet ....1984).TheydMdedttoersampleinlOnannalcontrols.IArtyd8m6n1ingindividuals anddellnltedemenllng Indlvlctualson\hebasi,of dementia score.Therllseerc hel's!Dundthat ltledementia index~atednegativelywithaDthepsyc:nomettlcmanures.Inc\ldingU- NART.However,Ina followup study\lalngthesamesample (Searto.1984),theNARTwasthe onlymellSllrllwhlch didnot.howsignifica nt performance dec linelordementingindividuals.but this WIS onlythecase when probabllcasesofdementia wereconslderecl separately.That Is, when possib le andprobabll casas werecombined,thereweresignificant dlnereoces in NART performsnc:elromtlm~lone 10time fwe.The authors however. suggest edthat subjectslabelled

"possIblecases ofdem8n~I'maynothave been dementing, but may havebeencu ••orlong- standinglow Ir.telligance.

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"

Brayne and Bearelsell (1990) conducted a larg.scale community study of 365 elderly women. The researchel"l!l compared NART performanceandpertorm.~on amini- neuropsycnologlcal lest battery (the CAMCOG).In womendiagnosedas damenting onthe CambridgeMentalDisorders01the ElderlyExamination(CAMDEX)withthose scoringwithInthe non11al rangeon thisdiagnosticinterview.Theytoundthat thosedllgnosedIS demantingsccred significantlylower onboththeCAMCOGandthe NAATthin(hose diagnosed as normal.

Howev6I,the 75·79 year oldsdiagnosed 83 mildtmoderatetydamentlngscoredslightly.!!!!Won the NAAT then those diagnosedISmildly demenllng.a~houghthe numbers of subjects were small.

Therewereseveral methodologicalproblemswiththis study.First,theresearchers did not adequatelycontrollor demographk:variability betweenthe groups(dementfngve. control).Thus, ifdamentlng subjectshad,forlnslance, lower education than controlsubjects,the observed group differenceIn NAAT perfonnance might bestbeexpleinedbypoor educatIon01demenUng subjects rather thanlack ofvalidity 01the NART.Secondly,theresearchers themselves poInted out that theirdiagnostic intervIew (theCAMDEX),Included the mini-neuropsychologicaltest bettery,the CAMCOO.Althoughthe diagnosiswas made priortocalculation01 CAMCOG scores.theimpression of perfonnaoce on these testsmay have biased the diagnoses towards dementia when In'act, a prop.Jltionof those subjecUlmaymerely have hadlong-standinglower Intelligence. In other words, some 01the "dementing"group may well have hadIong.standing lower Intelligencerath6r than dementia,and therefore wouldbeexpected 10score lower onII1e NARTthan those classltled liS nonnal,duetorower premorbid inlell1genc8.

One srudyfound that the NART e:ltlmatedpremorbldWAISFS1Q(usingthe Nelson,1982, regre"lon equation)signlfcantly dlsUngulshedbetween demamll"l!land normal elderly control subjec1s,withthe pBtlel'ltsample scoringlower than controlson the NART (Han et at.,1986).

However,the researcherscompared two other methods 01predictingWAIS FSIQ (theVocabulary subtesl 0' the WArS god the SGWRT, using Nelson& McKenna's,1975.regression equation) with the NAAT, andthey foundthe NART providedthehighest estimateof FSIO. The authors therefore concludedthat the NAAT was nottotally resistant to dementia, but W&9 the but premotbldIndicatorInvestigated Inthe study.

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2.

Afurtherstudywh~hquestioned the 'holding"abilities01theNART,ClOm!1aredtheNART withWilsonandhis eollellgues' (1979) demographic formula'sabWitytoe.stlt\'latepren'lOft»d intelligence(Stebbins81at.1987).They found Ihatttl.NART estimates lor their d«nentlng semple

ill •

122) differedfor moderatelyand severely dementingIndw!dulIlsthanlor mildly dementlngIndlvlduels and controls.However,the llu!tlors neglectedtomention which procedure lor measuringpremorbldIntemgenceINAAT vs.Wilson'sdemographic equation) was superior.

TheyconcludttdthaIalthoughtheNARTmay be•promisingeUnlceltool. its applicabilityto moderatelyor severely dementlngIndividualsmaybeHrnited.Indeed,itIsImprobable that W psychom etricmeasure wKIprovetobecomplete ly 'dementla·insen sitlve",butthe reeeerch to dale IndicateslhatIncompllifisonwithothercurrent methods01estimatingpremorbldJnlellJgence, the NARTseems tobethebestFurther,althoughthe results01this studysuggestthatII islikely lhatreadingabilitiesmaybeaffectedinseverely dernentlng IndivIduals,its primaryclinicaluseIs Intended tobewithpatientsintheeally stages 01dementia,where diagnosis Is typicallya problem,Further,thisstudy was summarized in abrief abstract withlimited InfoRnation,the autnersonlymentionedthat the groupswere equaled for eoucetcn.It IsthareforeImpossibleto determineil severe,moderate,and mild groupswerewell matched In terms01other demographic variablesknownto berelatedto10 (e.g"occtJIKIIon). II,lor instance, severely dementlng Indlvlduals were employedIn less prestIgiousoccupationsthan mildlydementlngIndividuals,the difference In NARTscoresmightbebestexplainedinferms o'long·standlnglowerIntelligencein the severelydemantinggroup,ratherthanIreduced Ibllity ofthe NAATto'hold' witl1Increased dementia savority,

In answer tothe potential problem ofth9NAAT nol 'holding'with someIndividuals.

Crawford and his colleagueshavedevelopeddemographicequallonstopredict NAAT errorscore (Crawford,Allan, Cochrane. & Parker,unpUblishedmanuscript).ThatIs, it maybeusefulto estimateNAAT ermr score to determine II observedNARTperformanceIII worse than8ll:pectecI givenen individual'sdemographicbackground,particularlyIIthe individualIsIn the severestages c!dementia.SII'lC9 demographicvariablesare correlated with la and are completelyfreefrom current cognitiveability,they couldbeusedtoprecllCtNART error scores.Further, iltheobtalnecl NARTerror scoreIssufficientlylargerthinthe predicted NAATerror score,the obtained9COl'8 shooldbeecepectInterms 01under8stlmltlngpremorbldla, assumingboth arevalid. The

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..

authors administered theNARTand collected demogrlllphlcdill(education,age, social CIISS, lind MX).from • large sample

l!'!•

659) of cognlti...8tt Intact subjects.Theyfound •slgnillcant mulllplt!correlltlonMtwMndemogrlphlcva ria b les and the NART(B -0.70 •

.e

<.00(1).Further, theyregressed demogrlphicvariables against NART 8trOf scores 10 develop regression equationstopredictNART10. The authors noted Ihalll the discrepancy between obtained and predicted NART error eccre was greater than 11.4 points, thIswouldbeIndicative thai an Individual's NART performancewusignificantly worse than wouldbe8xpeo:;:ted lrom hl9/her demographic background.

1.2.4.3. HART InComplIF'.onWithOth_ MMhoda of IJlatingulahlng Oementlng from Nondem..,t1ng lndlvldu••

Some c11nM;:aMhave used the WAISVocablilary SUbIa,! age·scaled 3COfatoestimate premOl'bldImelli>oltlJal functionIng.Studies have anown, however,thallhlsIndex Is Inferior to measures01word reading ability(I.e.•SGWAT and NART)lorthispurpose, lor both dementlng and depressed(ndivlduals (CraWfordet et,1988s:Crawford, Besson,Parker, Sutherlsnd&

Keen. 1987;Hsrt et at,1986; Nelson&McKenns, 1975). Nelsonsnd McKenna (1975) compared word resdlngsbllity as measuredbyIhe SGWRT,with performance on tho WAIS Vocabulary eubteet in a sample0198 hospitalizedcontrolsubjects with eXCra<erebraldisorders and 45 hospitalized demantlng subjects. They found that the mean Vocabulary age-scaled score ollhe dementlng subjects was significantly lower thanthe mean VocabUlaryaga-scaled score of thecoroml subjects. In comparison,the mean SGWRTscom01 dementlngsubjects was not significantly different lrom the mean SGWAT score of controls. Furtt1er,the rllsearchllr3 rllgressedbothSGWRT and Vocabulary subtast age·scaled scorasof control subjects aga(nsl control subjects'scores on WAIS FSIO,tocreateregression equationsto predicl WAIS FSIO from either NART error scores or Vocabulary subte91age-scaledscores. Individual subjects' sco~on SGWRTandlhelrage-9Cll1ed 9COres ontheVocabulary suble,twere then enteredInto theirrespective regressionequallonsto predict WAIS FSIO,and discrepancy scores were calculated (SGWAT predicted FSIQ - WAIS fSIO andVocabulal)' pradlctad FSIO- WAIS FSIO)_

The results showed that there was lessoverlap between domentingand control subjects' discrepancyscores when SGWRT WIS used topredictpramortlid WAIS Fsrothan when the Vocabulary subtest was usedto predict premortlid WAIS FSIO. The reseerchafs concludedthat

SL Al

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ABSTRACT

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ACKNOWLEDGEMENTS

Table of Contents

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