THE RELIABILITY OF STAGING AND GRADING OF BLADDER-TUMORS - IMPACT OF MISINFORMATION ON THE PATHOLOGISTS DIAGNOSIS

The influence of misinformation on the reliability of the histopatholo gical classification of bladder tumours was analysed. Four consultant pathologists assessed 40 biopsy specimens of bladder tumours staging i nvasion and grading the specimens according to the Bergkvist classific ation. A random sample of 20 specimens was accompanied by systematical ly distorted information (''bias''-unknown to the pathologists) about previous histological grading of the patient (bias group); the other 2 0 specimens were used as control group (non bias group). After 6 month s a second round with the same specimens was arranged to assess the in fluence of bias on the intraobserver variation. Using kappa (kappa) st atistics the chance corrected interobserver agreement rate was poor bo th in staging of invasion and grading according to the Bergkvist class ification (kappa < 0.50). The kappa values in the intraobserver study ranged from poor to excellent with a tendency towards lower kappa when the observer had been biased. The kappa values in the assessment of m alignancy were acceptable to excellent. False information did not affe ct the pathologists' diagnosis significantly.