False positive pregnancy tests in pediatric patients with augmentation enterocystoplasty

Our primary aim was to determine the prevalence of positive over-the-counter (OTC) pregnancy tests among pediatric female and male patients who had undergone augmentation enterocystoplasty. A secondary aim was to determine whether patient factors or urinalysis (UA) results were associated with false positive OTC pregnancy test results in patients with a history of augmentation enterocystoplasty.

Patients at a tertiary pediatric hospital who had previously undergone augmentation enterocystoplasty, Mitrofanoff appendicovesicostomy only, and age- and sex-matched controls were prospectively recruited. Urine samples were obtained, and two OTC pregnancy tests were conducted - OTC Test A reported the ability to detect pregnancy at hCG levels as low as 9.6 mIU/mL, while OTC Test B reported positive pregnancy test results at hCG levels ≥25 mIU/mL. A point of care (POC) pregnancy test and UA were also completed. Mann-Whitney U tests and Fisher's exact tests were used to assess whether patient factors or UA results were associated with false positive pregnancy test results.

Fifty pediatric patients were enrolled, including 20 with augmentation enterocystoplasty, 20 age- and sex-matched controls, and 10 with Mitrofanoff appendicovesicostomy only. Among the 20 patients who had undergone augmentation cystoplasty, 15 (75.0%) had positive pregnancy test results on OTC Test A, including 11/13 (84.6%) females and 4/7 (57.1%) males. No control patients or patients with Mitrofanoff appendicovesicostomy only had a positive test. No patients had positive pregnancy test results on OTC Test B or the POC test. While patients with augmentation enterocystoplasty were significantly more likely to test positive for blood (p = 0.01), nitrate (p = 0.03), and leukocytes (p < 0.0001), these factors were not significantly associated with false positive pregnancy results. No patient factors or UA results were associated with increased likelihood of false positive OTC pregnancy test results.

These findings indicate that sensitive OTC pregnancy tests that detect low quantities of hCG in urine may result in false positive results among patients who have undergone augmentation enterocystoplasty. Female patients of reproductive age with bladder augmentations should be counseled regarding appropriate pregnancy testing options. Additional research is needed to determine the mechanism responsible for false positive pregnancy tests in this patient population.