Comparative analysis of DNA flow cytometry and cytology of bladder washings: Review of discordant cases

DNA analysis is becoming an important diagnostic and prognostic adjunct tes t in urinary cytology. The aim of this study was to compare the results of DNA flow cytometry (FCW) with the cytologic diagnosis of bladder washings ( BW). DNA ploidy was evaluated in 251 BW. In 65 cases, follow-up surgical bi opsies were available. Cytology results, were classified as positive and ne gative, and FCM results were categorized as diploid and aneuploid. Both tes ts were evaluated independently. Cases were defined as discordant if the cy tology was negative and FCM was aneuploid, or if the cytology was positive and FCM was diploid. All discordant cases were reviewed, and positive predi ctive values (PPV) for FCM and cytology,were calculated for cases with foll ow-up biopsy results. Cytologic evaluation classified 181 cases as negative , with 175 of them diploid and 6 aneuploid; and 70 as positive, with 53 of them diploid and 17 aneuploid. Overall, there were 59 discordant cases (23. 5%, with a confidence limit of 18.2-28.8%). Of 6 aneuploid/ cytology-negati ve cases, biopsies were available in 4 cases and showed one grade 1, two gr -ade 2, and one grade 3 unrothelial carciroma (UC). Reanalysis of these 6 c ytology specimens showed 1 case that should have been interprered as positi ve (false negative), 4 true negatives, and 1 polyoma virus infection. Out o f 53 diploid/cytology-positive cases, biopsies three available in 45 cases and showed nine grade 1, 14 grade 2, three grade 3 UCs, 11 UCs in situ, and eight negative biopsies. The PPV for cytology was 85%, and the PPV for FCM was 95%. We concluded that FCM, which requires a large number of cells, of ten cannot detect small aneuploid populations, which a,are present particul arly in cases of UC insitu. (C) 2000 Wiley-Liss, Inc.