title: Multicenter determination of optimal interobserver agreement using the Fuhrman grading system for renal cell carcinoma: Assessment of 241 patients with > 15-year follow-up.
abstract: BACKGROUND
  The Fuhrman system is the most widely used nuclear grading system for renal cell carcinoma (RCC). Although Fuhrman nuclear grade is widely accepted as a significant prognostic factor, its reproducibility, as reported in the limited number of series available in the literature, appears to be low.
  
  
  METHODS
  Between 1980 and 1990, 255 cases of RCC (pT1-3bN0M0) were treated with radical nephrectomy at the Department of Urology, University Hospital, Strasbourg, France. In a retrospective multicenter study, 3 pathologists independently classified 241 of these 255 cases according to the Fuhrman grading system. The authors searched for optimal interobserver agreement by collapsing the grading system to a three-tiered scheme and then to a two-tiered scheme. In addition, overall survival curves were generated according to the classic four-tiered scheme and also according to the best collapsed scheme. The kappa index was used to assess the level of agreement between each pair of observers, and the Cox model was used for multivariate survival analyses.
  
  
  RESULTS
  The mean interobserver kappa value was 0.22 (range, 0.09-0.36). The best concordance was obtained by collapsing to a system in which low-grade (Grade 1-2) disease was compared with high-grade (Grade 3-4) disease. Doing so improved the mean interobserver kappa value to 0.44 (range, 0.32-0.55). Fuhrman grade was an independent prognostic factor for all 3 pathologists (P = 0.01, P < 0.0001, and P = 0.004, respectively), and nuclear grade continued to have independent prognostic value after the optimal collapsing algorithm was performed (P = 0.004, P = 0.0003, and P = 0.005).
  
  
  CONCLUSIONS
  Collapsing of the Fuhrman grading system to a two-tiered scheme led to an improvement in interobserver agreement while preserving the independent prognostic value of nuclear grade.
authors.affiliation: Department of Urology, University Hospital, Strasbourg, France. herve.lang@chru-strasbourg.fr
authors.forename: Hervé
authors.initials: H
authors.lastname: Lang
authors.forename: Véronique
authors.initials: V
authors.lastname: Lindner
authors.forename: Marc
authors.initials: M
authors.lastname: de Fromont
authors.forename: Vincent
authors.initials: V
authors.lastname: Molinié
authors.forename: Hervé
authors.initials: H
authors.lastname: Letourneux
authors.forename: Nicolas
authors.initials: N
authors.lastname: Meyer
authors.forename: Mael
authors.initials: M
authors.lastname: Martin
authors.forename: Didier
authors.initials: D
authors.lastname: Jacqmin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002292:Carcinoma, Renal Cell / Q000453:epidemiology* / Q000401:mortality / Q000473:pathology* / Q000601:surgery; D005260:Female; D005602:France / Q000453:epidemiology; D006801:Humans; D007680:Kidney Neoplasms / Q000453:epidemiology* / Q000401:mortality / Q000473:pathology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009392:Nephrectomy / Q000379:methods; D015588:Observer Variation; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012307:Risk Factors; D016019:Survival Analysis