False-positive urine pregnancy screening tests are uncommon in the hospital setting among patients with bowel-containing urinary tract reconstruction

Abstract

Purpose: False-positive urine pregnancy screening tests (UPST) have been reported among patients with bowel-containing urinary reconstruction (BCUR). However, the true frequency of such inaccurate results, which have been attributed to urinary mucous or other proteins interfering with or mimicking the binding of beta-HCG in the assay, is unknown in this population. We sought to determine the incidence of false-positive pregnancy screening tests among this patient population at our institution.

Materials and methods: Using existing databases of patients with spina bifida, bladder exstrophy, and genitourinary rhabdomyosarcoma, we identified female patients with BCUR who had UPST over a 10-year period as screening prior to procedures or imaging. Patient and test result information was recorded.

Results: A total of 120 patients with a history of BCUR were identified: 33 with spina bifida, 73 within the exstrophy-epispadias complex (EEC), and 14 with genitourinary rhabdomyosarcoma. Of this group, 46 patients (38%) had at least one UPST during the study period; 15 had 1 UPST, 6 had 2 UPSTs, 4 had 3 UPSTs, and 21 had greater than 3 UPSTs, for a total of 244 UPST in this cohort. UPSTs used at our institution included Sure-Vue brand and Alere brand (HCG sensitivity 20 mIU/ml). Types of BCUR included ileal enterocystoplasty in 25 patients, colon enterocystoplasty in 6, stomach enterocystoplasty in 5, composite enterocystoplasty in 7, and continent catheterizable channel alone (e.g. Yang-Monti, appendicovesicostomy) in 3 patients. Of the 244 UPSTs in patients with BCUR, zero (0%) were positive.

Conclusions: Despite reports in the literature that false-positive UPST are common among patients with bowel-containing urinary diversions, we found no positive UPST among patients with BCUR in the healthcare setting. False-positive UPST in the home setting may be due to variability in sensitivity thresholds, binding agents, technical errors in test technique, kit quality control, or other factors.

Keywords: Bowel-containing urinary reconstruction; Enterocystoplasty; Urinary pregnancy tests.