Screening and monitoring for bladder cancer: refining the use of NMP22.

PURPOSE While detecting bladder cancer, bladder tumor markers demonstrate improved sensitivity compared with urinary cytology but the current limitation is the low specificity and positive predictive value, that is high false-positive rate. We examined the clinical categories of the false-positive results, established relative exclusion criteria, and recalculated the specificity and positive predictive value of this assay with these criteria. MATERIALS AND METHODS A total of 608 patients considered at risk for bladder cancer presented to a urology clinic and submitted a single urine sample. Of the 608 patients 529 (87%) presented with de novo hematuria or chronic voiding symptoms without a diagnosis of bladder cancer. There were 79 (13.0%) patients being monitored with a known history of bladder cancer. Each urine sample was examined via cytology, urinalysis, culture and NMP22 protein assay. All patients underwent office cystoscopy, and transurethral resection and/or biopsy if a bladder tumor was suspected. RESULTS Of the 608 patients 226 (37.2%) presented with microscopic hematuria, 143 (23.5%) with gross hematuria and 239 (39.3%) had chronic symptoms of urinary frequency or dysuria. There were 52 (8.6%) patients who had histologically confirmed bladder cancer. Of these 52 cancers NMP22 detected 46 (88.5%), whereas cytology identified only 16 (30.8%). When atypical cytology was considered positive, cytology detected 32 (61.5%) cases. In the 135 patients with increased NMP22 values the 46 identified tumors were accompanied by 89 false-positive values yielding a specificity of 83.9% and a positive predictive value of 34.1%. These false-positive results were divided into 6 clinical categories. Exclusion of these categories improved the specificity and positive predictive value of NMP22 to 99.2% and 92.0%, respectively, yielding results similar to urinary cytology (99.8% and 94.1%). CONCLUSIONS Awareness and exclusion of the categories of false-positive results can increase the specificity and positive predictive value of NMP22, enhancing the clinical use of this urinary tumor marker.