[Reliability of routine cytological diagnosis in bladder cancer]

To establish the reliability of three cystopathologists for cytological diagnosis of primary bladder tumors.

Pre-operative voided urine specimens of 71 patients with bladder cancer and 55 healthy controls were retrospectively and blindly reviewed by 3 independent cytologists, and their results--positive for bladder cancer, negative or inconclusive--were compared with each other. The estimation of the interobserver agreement was calculated using the weighted kappa-coefficient (k). A multivariative analysis was carried out to identify the factors associated with the disagreement among the three observers. The sensitivity and specificity for each of the participants were calculated in order to clearly identify the origin of the disagreement, in terms of the performance of the diagnostic test in the hands of each observer. A comparison of the overall diagnostic performance was made by plotting sensitivity versus 1-specificity.

The weighted k coefficient among observers was 0.46. The multivariative analysis did not identify any variable that could have caused such disagreement. Large differences in sensitivity and specificity were detected between observer number 1 (sens., 0.90, spec., 0.45) and observers number 2 (sens., 0.67, spec., 0.72) and number 3 (sens., 0.71, spec., 0.80), but the overall diagnostic performance (sensitivity vs 1-specificity) was superimposable in the three cases (p = ns).

Simple, reproducible and agreed-on diagnostic criteria should be established to yield reliable results in a group of cytologists. The consideration of individual diagnostic performances can give a false idea of homogeneity between observers. In this field, concordance analysis makes quality control reliable and should be a routine procedure of any pathology department.