False-positive pregnancy tests in patients with enterocystoplasties

To determine the incidence and causes of false-positive pregnancy tests in patients with enterocystoplasties. Patients and methods In a pilot study, 15 consecutive patients (both sexes, with any type of urinary diversion) provided a urine sample for testing using the Clearview pregnancy test (Unipath Ltd, Bedford, England). False-positive results occurred only in patients with continent reservoirs; patients with ileal conduits produced no false-positive results and were excluded from the main study. The main study included 23 patients with a urinary reservoir constructed partly or solely of large bowel or ileum, who provided urine and blood samples for the assay of beta human chorionic gonadotrophin and protein. Each urine sample was also analysed with the Clearview test.

In the pilot study, three men and two women had positive pregnancy test results. In the main study, 14 patients had a positive Clearview test (nine women and five men). One women was found to be pregnant and was therefore excluded from further analysis, giving a false-positive rate of 57%. There was no difference in the type of reservoir, urine biochemistry and urine analysis results between the positive and negative groups. Frozen/thawed samples all tested negatively. Conclusion It is possible that the mucus produced in enterocystoplasties may be interfering with the pregnancy test. Patients should be aware of this and not rely on commercial test kits. There is some potential that this test system could be adapted for measuring mucus production in urinary diversions.