Risk of malignancy assessment for the Paris System for reporting urinary cytology

Abstract

The Paris System for reporting urinary cytology was introduced in 2013 and has a global impact. In our study, we assess the risk of malignancy (ROM) for each diagnostic category and our diagnostic accuracy in urinary cytology. We have conducted a prospective study during 2019, including only new cases of urothelial neoplasms, all of them with subsequent histology. The risk of malignancy for each category was calculated and the diagnostic accuracy parameters were estimated in correlation with histology. The estimated risk of malignancy (ROM) for high-grade neoplasms was 0% for TPS1, 6.5% (2/31) for TPS2, 36% (9/25) for TPS3, 65% (13/20) for TPS4, 100% (18/18) for TPS5 and 16% (2/13) for TPS6. Accuracy parameters for high-grade urothelial carcinoma (HGUC) were evaluated in two ways, in the first considering TPS3 as a negative and in the second as a positive result and the values were: sensitivity 70% vs 90.9%, specificity 89.3% vs 65.2%, PPV 81.5% vs 63.5%, NPV 82% vs 91.5% and diagnostic accuracy 81.8% vs 75.4%. For low-grade urothelial neoplasm (LGUN) diagnosis, sensitivity was 42%, specificity 76%, PPV 71%, NPV 48.6% and diagnostic accuracy 56%. The risk of malignancy for the TPS categories has a clinically meaningful gradation and the effectiveness of urinary cytology is improved by the application of the Paris System.