The diagnostic reliability of urinary cytology: a retrospective study.

The aim of this study was twofold. The first aim was to estimate the diagnostic reliability of urinary cytology for detection and management of urothelial neoplasms by using a specific preserving fluid for sample collection, and the liquid-based thin layer method for specimen preparation, the estimate was based on the correlation between the cytological findings of 10,000 non-hospitalized patients, and their histological diagnoses. A second aim was to compare the reliability of two instruments for thin-layer preparation, i.e., TP2000, TP3000, capable of processing the specimens at very different rates. The preservation of cell structure is ameliorated by the procedure of sample collection and treatment here described. This allows a more accurate reading of LBC slides as shown by: (a) the significant concordance between cytological and histological diagnosis (92%); (b) the significant number of low-grade urothelial carcinomas (20.5%) revealed by urinary cytology and validated by histologic diagnosis; (c) the low rate (8%) of misjudgement of cytological diagnosis reached in this study. The quality of performances of the two instruments tested for thin-layer preparation, i.e., TP2000 and TP3000, is statistically comparable. We recommend the procedure that makes use of preserving fluid for sample collection (cytolyt™) and treatment (preservcyt ™) as here described. We also recommend the use of thin-layer method for specimen preparation since it allows a more uniform distribution of the cells on the support with reduction of overlapping phenomena. Finally, economic considerations suggest the preferential use of Thin Prep 3000.