Comparison of urine collection methods for evaluating urinary nuclear matrix protein, NMP22, as a tumor marker

Purpose: The nuclear matrix protein, NMP22, has been shown to be a useful tumor marker for identifying patients with a high likelihood of rapid recurrence of transitional cell carcinoma of the urinary tract after surgical treatment. Currently measurement of NMP22 involves 3 urine voids collected during a 24-hour period, which are pooled and assayed as a single sample. This study was performed to determine whether any single void would yield similar results to the pooled 3-void sample. Materials and Methods: A total of 2,018 urine samples (3 voids per sample) was included in the study. All analyses were performed using the nonparametric Wilcoxon signed rank test for matched pairs. Results: Analysis showed that the NMP22 level of a single void collected between midnight and noon was similar to the NMP22 level of the pooled 3-void sample. Receiver operating characteristics curves of the midnight-to-noon single void and the pooled 3-void sample were similar for predicting recurrence postoperatively in patients with urinary tract transitional cell carcinoma. Conclusions: One void collected between midnight and noon compares favorably with the current 3-void collection method for determining NMP22 levels in urine.