Impact of the Paris system for reporting urine cytopathology on predictive values of the equivocal diagnostic categories and interobserver agreement

BACKGROUND: The Paris System (TPS) acknowledges the need for more standardized terminology for reporting urine cytopathology results and minimizing the use of equivocal terms. We apply TPS diagnostic terminologies to assess interobserver agreement, compare TPS with the traditional method (TM) of reporting urine cytopathology, and evaluate the rate and positive predictive value (PPV) of each TPS diagnostic category. A survey is conducted at the end of the study. MATERIALS AND METHODS: One hundred urine samples were reviewed independently by six cytopathologists. The diagnosis was rendered according to TPS categories: negative for high-grade urothelial carcinoma (NHGUC), atypical urothelial cells (AUC), low-grade urothelial neoplasm (LGUN), suspicious for high-grade urothelial carcinoma (SHGUC), and high-grade urothelial carcinoma (HGUC). The agreement was assessed using kappa. Disagreements were classified as high and low impacts. Statistical analysis was performed. RESULTS: Perfect consensus agreement was 31%, with an overall kappa of 0.362. Kappa by diagnostic category was 0.483, 0.178, 0.258, and 0.520 for NHGUC, AUC, SHGUC, and HGUC, respectively. Both TM and TPS showed 100% specificity and PPV. TPS showed 43% sensitivity (38% by TM) and 70% accuracy (66% by TM). Disagreements with high clinical impact were 27%. Of the 100 cases, 52 were concurrent biopsy-proven HGUC. The detection rate of biopsy-proven HGUC was 43% by TPS (57% by TM). The rate of NHGUC was 54% by TPS versus 26% by TM. AUC rate was 23% by TPS (44% by TM). The PPV of the AUC category by TPS was 61% versus 43% by TM. The survey showed 33% overall satisfaction. CONCLUSIONS: TPS shows adequate precision for NHGUC and HGUC, with low interobserver agreement for other categories. TPS significantly increased the clinical significance of AUC category. Refinement and widespread application of TPS diagnostic criteria may further improve interobserver agreement and the detection rate of HGUC.