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

Abstract

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. 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. 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 20mIU/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. 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.