RESUMEN
The urine fluorescence in situ hybridization (FISH) assay (UroVysion™), with the current scoring criteria, has a higher sensitivity than routine cytopathology but a lower specificity. Among 215 urine FISH tests we performed, 45 had associated histopathology and clinical follow up. In this study, a cell with four signals for each probe was classified as a uniform tetraploid cell (UTC); a presumed reparative cell which is currently classified as an abnormal cell in the FDA approved assay. By using the existing criteria, the tests were scored as positive or negative before and after exclusion of the UTCs. Before the exclusion, 24 positive, 13 negative, seven false positive, and one false negative result were obtained with 96% sensitivity and 65% specificity. After the exclusion, the results changed to 22 positive, 19 negative, one false positive, and three false negatives resulting in a 88% sensitivity of 88% and a 95% specificity; a significant improvement in the specificity. We conclude that exclusion of the UTCs as abnormal cells would result in a more solid performance of the FISH assay.