BACKGROUND:UroVysion is a US Food and Drug Administration–approved fluorescence in situ hybridization (FISH) probe set for use in the detection of recurrent urothelial carcinoma and in patients with hematuria. The objective of the current study was to evaluate the usefulness of UroVysion as a reflex test in patients with a suspicious urine cytology diagnosis. The rationale was that a more aggressive workup might be indicated in patients with a suspicious cytology diagnosis and positive UroVysion test.METHODS:The study population included 161 urine specimens diagnosed as suspicious over a period of 12 months. The sensitivity, specificity, negative predictive value (NPV), and positive predictive value (NPV) were calculated based on the histologic and cystoscopic correlation.RESULTS:The results using the reporting criteria suggested by the manufacturer demonstrated a sensitivity of 68.3%, a specificity of 39.7%, a PPV of 56.8%, and a NPV of 51.9%. The results using the presence of any cytogenetic abnormality as a positive FISH test demonstrated a sensitivity of 82.9%, a specificity of 21.7%, a PPV of 54.8%, and an NPV of 51.7%.CONCLUSIONS:A negative UroVysion test did not rule out the presence of low‐grade or high‐grade urothelial carcinoma in urine specimens diagnosed as suspicious. The use of less strict criteria dramatically increased the sensitivity of UroVysion FISH; however, there was a marked decrease in specificity noted. The results in this current study appear to indicate that a more aggressive workup of patients with a suspicious cytology, positive UroVysion result, and negative cystoscopic evaluation is not currently justified. Cancer (Cancer Cytopathol) 2009. © 2009 American Cancer Society.