Is conventional urinary cytology still reliable for diagnosis of primary bladder carcinoma? Accuracy based on data linkage of a consecutive clinical series and cancer registry.

OBJECTIVE: Reported urine cytology accuracy, particular sensitivity, is highly variable. We evaluated the accuracy of urinary cytology for primary bladder cancer using population data linkage to provide valid estimates. STUDY
DESIGN: Consecutive cytology tests processed through a major service between January 2000 and December 2004 were linked to a regional population cancer registry (allowing outcome ascertainment). Sensitivity and specificity were calculated using different thresholds, based on standardized reporting categories (C1 = negative, C2 = reactive, C3 = atypical, C4 = suspicious, C5 = malignant, Cx = inadequate).
RESULTS: Cancer registry matching of 2,594 tests revealed 130 incident bladder cancers, of which 97 occurred within 12 months of cytology and were included in calculating accuracy. Sensitivity (C3-C5 considered positive) ranged between 40.2 and 42.3%, and specificity was 93.7-94.1%. If C3 results are counted as negative, sensitivity estimates reduced to 24.7-26.0%. The positive predictive value of a C3, C4 or C5 report was 11.7, 39.2, and 66.6%, respectively. High tumor grade was associated with significantly higher sensitivity compared to low and intermediate grades combined (p = 0.02).
CONCLUSION: Urine cytology is highly specific but has intermediate sensitivity, indicating that it has a role in adjunct diagnosis, but not in screening for primary bladder cancer. C3 results should be considered 'positive' and further investigated, and all positive results should prompt further intervention.