The Impact of The Paris System for Reporting Urinary Cytology Implementation: A Comparative Study with Histologic Follow-Up of 998 Cases

Summary: Introduction: The Paris System (TPS) for Reporting Urinary Cytology was implemented in our institution in 2017. This study aims to evaluate the performance of TPS by comparing it with histologic follow-up. Materials and Methods: Voided and instrumented urine cytology specimens (2017-2022) were compared with follow-up histology (within 6 months). The risk of high-grade malignancy (ROHM), sensitivity (SN), specificity (SP), positive predictive value (PPV) and negative predictive value (NPV) were calculated. In the analysis, urothelial carcinoma in-situ and HGUC were considered high-grade malignancies (HGM). Results: A total of 998 cases were included, and the patients had a median age of 72 years. There was a 2.3% non-diagnostic rate, while 57% of cases were Atypical Urothelial Cells (AUC) and above (AUC+, Table 1). The ROHM is within the range of most published literature. Among suspicious for high-grade urothelial carcinoma (SHGUC) and high-grade urothelial carcinoma (HGUC) cases with negative histology, 16 had HGM after more than 6 months. The categories of urines with degeneration and HGM were: 59.5% AUC, 23.8% NHGUC, 11.9% SHGUC, and 4.7% non-diagnostic. As expected, there is an inverse relationship between SN and SP when considering AUC+ to HGUC only as positive results (Table 2). SHGUC and HGUC both have high PPV. Conclusions: Our study is one of the largest in evaluating the implementation of TPS with histologic follow-up. There is a relatively high ROHM among all categories, which is partly explained by our tertiary referral center practice. The presence of degeneration in those with HGM could have swayed the diagnosis into indeterminate categories. The higher threshold and stricter criteria when evaluating atypia likely increased the specificity, but at the same time decreased the sensitivity from AUC+ to SHGUC+. Overall, the high specificity of TPS amplifies the role of urine cytology in providing unequivocal diagnoses.