Evaluation of the Implementation and Diagnostic Accuracy of the Paris Classification for Reporting Urinary Cytology in Voided Urine Specimens: A Cyto-Histological Correlation Study in a Cancer Center

Introduction: The Paris classification highlights the need to focus on accurately identifying high-grade urothelial carcinoma (HGUC). Herein, we aimed to assess the overall implementation and diagnostic performance of the Paris classification for reporting urinary cytology in a cancer center. Methods: All urinary cytology reports from July 2018 to December 2019 were collected (n = 1,240). Only voided urine samples were included (n = 1,180). Risk of high-grade malignancy (ROHM) was calculated for each Paris category. The diagnostic performance of urinary cytology was assessed, including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy. Results: The distribution of categories was: 0.3% unsatisfactory, 90.5% negative for HGUC, 5.6% atypical urothelial cells (AUC), 1.6% suspicious for HGUC, 1.9% HGUC, and 0.1% other malignancies. No diagnosis of low-grade urothelial neoplasia was given. The ROHM was 21.4% for negative for HGUC, 66.7% for AUC, 91.7% for suspicious for HGUC, and 100% for HGUC. When using suspicious for HGUC as a cutoff, the diagnostic performance of urinary cytology in identifying HGUC histology was 46% sensitivity, 98% specificity, 96% PPV, 68% NPV, and 74% accuracy. Conclusion: Specificity of urinary cytology was very high (with only 1 false-positive result), which is important since this will trigger a clinical intervention. The ROHM for each category was in accordance with literature, except for AUC where ROHM was slightly higher (66.7%). This may be explained by the study population characteristics (cancer center; many patients treated with intravesical therapies; lack of clinical annotation for patients referred from outside institutions).