Evaluation of the BTA tests for the detection of bilharzial related bladder cancer: the Cairo experience.

Objective: To evaluate the clinical performance of the BTA stat test and the BTA TRAK assay in the diagnosis of bilharzia-related bladder cancer and to calculate a new 'Egyptian' cut-off value for the BTA TRAK (quantitative) assay.

Methods: Urine samples of 149 individuals were tested for the presence of the human complement factor H-related protein, the antigen detected by the BTA stat and BTA TRAK tests. The group consisted of 53 healthy volunteers, 20 patients with active bilharziasis, 11 patients with other urologic disorders including prostate cancer, and 65 patients with histologically proven bladder cancer. All samples were obtained prior to surgery or therapy.

Results: The BTA stat test was positive in 64 of 65 samples from patients with bladder cancer, for an overall sensitivity of 99%. With a BTA TRAK assay cut-off of 60 U/ml (set at 97% specificity in the healthy population), the sensitivity of the TRAK assay was 94%. There was no statistically significant difference between the sensitivities of the two BTA tests in patients diagnosed with squamous cell carcinoma and those with transitional cell carcinoma. The overall specificity of the BTA stat test was 67% ranging from 15% in patients with bilharziasis to 94% in healthy volunteers. The overall specificity of the TRAK assay was 66%, again with negative results in 15% of the patients with bilharziasis.

Conclusions: The BTA stat test and TRAK tests are extremely sensitive in the detection of bladder cancer in the Egyptian population. Positive results (85%) are also observed in patients with active bilharziasis, which often leads to bladder cancer. Longitudinal follow-up of these positive cases is needed to determine whether these positive results are false or predictive of bladder cancer.