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

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.

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.

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.

One void collected between midnight and noon compares favorably with the current 3-void collection method for determining NMP22 levels in urine.