Importance of urinary cytology and future role of flow cytometry

A study recently completed in our laboratory evaluated the role of flow cytometry in comparison with urinary cytology in a clinical practice setting to ascertain the utility of this new method in routine diagnostic pathology. In patients being followed up for known bladder cancer, urinary cytology yielded a positive result in 85 per cent of cases. Flow cytometry yielded a 74 per cent positivity rate. The diagnostic accuracy of the two modalities combined was 98 per cent. The lower diagnostic yield from flow cytometry occurred in patients treated with topical chemotherapy for bladder cancer. This apparent false negative result of flow cytometry may be due to paucity of cells from epithelial denudation by the topical agents, inhibition of tumor growth by the chemotherapeutic agent, or masking of small aneuploid cell populations by a large inflammatory cell population. Our results suggest that urinary cytology and flow cytometry are complementary laboratory tests in the diagnostic evaluation of bladder cancer patients in clinical practice.