The reliability of staging and grading of bladder tumours. Impact of misinformation on the pathologist's diagnosis.

Abstract

The influence of misinformation on the reliability of the histopathological classification of bladder tumours was analysed. Four consultant pathologists assessed 40 biopsy specimens of bladder tumours staging invasion and grading the specimens according to the Bergkvist classification. A random sample of 20 specimens was accompanied by systematically distorted information ("bias"-unknown to the pathologists) about previous histological grading of the patient (bias group); the other 20 specimens were used as control group (non bias group). After 6 months a second round with the same specimens was arranged to assess the influence of bias on the intraobserver variation. Using kappa (kappa) statistics the chance corrected interobserver agreement rate was poor both in staging of invasion and grading according to the Bergkvist classification (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 malignancy were acceptable to excellent. False information did not affect the pathologists' diagnosis significantly.