Use of ThinPrep monolayer technique and cytospin preparation in urine cytology: a comparative analysis

We compared the ThinPrep (TP) technique to the cytospin (CS) preparation in the cytological diagnosis of urine by processing 79 specimens by these two techniques. Ten cases were positive for malignancy (six high grade (HG)/carcinoma in situ; four low grade (LG) transitional cell carcinomas (TCC)). Forty-eight cases were within normal limits (59%) and 21 cases had atypical cytological features (19%). The TP technique was better in terms of a cleaner background with fewer obscuring inflammatory cells and blood and with a more even distribution of cells. In general, the cytomorphology was comparable in both techniques. However, in cases with malignancy, CS was relatively superior in the cytomorphologic details; in TP, the diagnostic cells were mostly dispersed as single cells with loss of architectural features and were difficult to find. Artifactual empty spaces and air-drying were more frequently present in TP. In cases contaminated with squamous cells, the urothelial cells were difficult to find in TP. Screening time was comparable for both techniques. In conclusion, to avoid false-negative diagnosis, CS would be complementary to the TP technique in malignant cases and, in particular, those with low cellularity.