Progrèsenurologie(2018)28,239—240
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LETTER TO EDITOR
Reproducibility of the American Association for the Surgery of Trauma scaling for renal injury:
Methodological issue to avoid misinterpretation
Reproductibilité de l’Associationaméricainepour la chirurgiedelamiseàl’échelledestraumatismespour les lésions rénales : question méthodologique pour éviterunemauvaiseinterprétation
Keywords Reproducibility;TheAmericanAssociationfor theSurgeryofTrauma(AAST);OrganInjuryScale(OIS);
Methodologicalissue
Motsclés Reproductibilité;Associationaméricainepour lachirurgiedutraumatisme(AACT);Échelledelésions d’organes(ELO);Questionméthodologique
Deareditor,IwasinterestedtoreadthepaperbyPhanQB andcolleaguespublishedinProgUrol2017Nov.1TheAmer- ican Association for the Surgery of Trauma (AAST) Organ Injury Scale (OIS) is themost usedclassification for renal trauma.Thepurposeoftheauthorswastoassessthesub- jectivityofAASTscaling.ComputedTomography (CT)scan were analyzed and injuries graded according toAAST OIS independently by a senior radiologist, a senior urologist who was blind to clinical data and a resident urologist.
They reported that ninety-seven patients had 101 renal injuries: low grade in 58.4% (11.9% grade I, 17.8% grade II,28.7%gradeIII)andhighgradein41.6%ofcases(23.6%
gradeIVand17.8%gradeV).Theagreementwasfairwith Kappa coefficient at 0.36. The agreement was moderate inseveritysub-divisionanalysis(loworhighgrade):Kappa coefficient at 0.59. There was a disagreement in 49.5%
betweenthe seniorurologist’s andthesenior radiologist’s ratings[1].
However,itiscrucialtoknowthattwoimportantweak- nesses of kappa are as follows. First, it depends on the prevalenceineachcategory,whichmeansitcanbepossible tohave differentkvalueshavingthesamepercentagefor bothagreementanddisagreementcells.Table1showsthat inboth(a)and(b)situations,theprevalenceofagreement cellsare90%andofdisagreementcells, 10%;however,we get differentkappa values(0.44asmoderate and 0.80as verygood,respectively).Kappavaluealsodependsonthe numberofcategories[2—3].
Table1 Limitation of kappa for comparison of two observers’diagnoseswithdifferentprevalenceinthetwo categories.
Observer1 Low grade
High grade
Total(%) Situation(a)
Observer2 Lowgrade 85 5 90
Kappa=0.44 Highgrade 5 5 10
Total 90 10 100
Situation(b)
Observer2 Lowgrade 45 5 50
Kappa=0.80 Highgrade 5 45 50
Total 50 50 100
Inbothsituationsa&b,theprevalenceofconcordancecellsare equalto90%(Bolds),however,wegetdifferentkappavalue.
They concluded that AAST OIS for renal trauma suf- fersfromsubjectivity.Suchconclusionshouldbesupported by the above mentioned methodological and statistical issues.Otherwise,misinterpretation ofthe findingcannot beavoided.
Disclosureofinterest
Theauthordeclaresthathehasnocompetinginterest.
References
[1]PhanQB,MoureyE,EstivaletL,DelattreB,BardetF,etal.Reli- abilityandreproducibilityoftheAmericanAssociationforthe SurgeryofTraumascalingforrenalinjuryandimpactonradio- logic follow-up. Prog Urol 2017, http://dx.doi.org/10.1016/
j.purol.2017.09.013[pii:S1166-7087(17)30565-1].
[2]SzkloM,NietoFJ:.Epidemiologybeyondthebasics.2ndedition Sudbury,MA:JonesandBartlettPublisher;2007.
[3]Sabour S. Spinal instability neoplastic scale: methodologic issues to avoid misinterpretation. AJR Am J Roentgenol 2015;204(4):W493.
240 Lettertoeditor S.Saboura,b,∗
aDepartmentofClinicalEpidemiology,Schoolof PublicHealth,ShahidBeheshtiUniversityof MedicalSciences,Tehran,Iran
bSafetyPromotionsandInjuryPrevention ResearchCenter,ShahidBeheshtiUniversityof MedicalSciences,Tehran,Iran
∗Correspondenceat:ChamranHighway,Velenjak, DaneshjooBlvd,DepartmentofClinical Epidemiology,SchoolofHealth,SafetyPromotion
andInjuryPreventionResearchCenter,Shahid BeheshtiUniversityofMedicalSciences,Tehran, 198353-5511Iran.
E-mailaddress:[email protected] Availableonline22March2018
https://doi.org/10.1016/j.purol.2018.01.003
1166-7087/©2018ElsevierMassonSAS.Allrightsreserved.
