Urinary BTA: indicator of bladder cancer or of hematuria.

BACKGROUND: In this study, we investigated the influence of hematuria on the performance of the bladder tumor antigen (BTA) tests in a clinical cohort and in an experimental model.
MATERIALS AND METHODS: Urine samples from a cohort of 126 subjects (64 with BCa and 62 controls) were analyzed by ELISA for hemoglobin and BTA. The experimental model involved the spiking of urine with blood from the same subject, and hemoglobin, red blood cell count, and BTA levels (BTA stat© and BTA-TRAK©). BTA-TRAK© analyses were also performed on serum samples obtained from 40 subjects (20 with confirmed with BCa).
RESULTS: In the 126 subject cohort, correlation between hemoglobin and BTA was 0.732. Of the 64 BCa samples, 72 % had a positive BTA assay, but 47 % of controls were also positive. The sensitivity and specificity of BTA to detect BCa was 72 and 53 %, respectively. Hematuria, measured by urinary hemoglobin, was a better indicator of BCa with 75 % sensitivity and 90 % specificity. Spiking of BTA-negative urine samples with as little as 1 μl/10 ml was enough to produce a positive BTA test. High levels of BTA were found equally in the serum of subjects with or without BCa (mean BTA levels 355,159 vs. 332,329 U/ml, respectively).
CONCLUSIONS: Rather than detecting a bladder tumor antigen, urinary BTA assays may be measuring serum cFH introduced by bleeding, a common presenting factor in BCa subjects. The presence of hematuria in subjects without malignant disease can result in false-positive BTA assays.