Prospective cohort study investigating the reliability of the AmnioSense™ method for detection of spontaneous rupture of membranes

Objective: This study investigated the reliability, sensitivity and specificity of a commercially available absorbent pad, AmnioSense™, compared with speculum examination for detection of spontaneous ruptured membranes (SRM). Design: Prospective cohort study. Setting: Antenatal Day Unit (ADU) of a UK inner-city teaching hospital. Population: Women attending the ADU with a history of suspected ruptured membranes between 18 and 42 weeks of gestation. Methods: Eligible women were asked to use the absorbent pad in accordance with the manufacturer's instructions. A midwife recorded the result. A second midwife performed a speculum examination according to unit protocol. Results were entered onto a password-protected study-specific database. Both midwives were blind to the other test result. Main outcome measures: Comparability between the index test (AmnioSense™) and reference standard (speculum). Results: A total of 157 women were recruited and results were analysed in 139 cases. Median gestational age at recruitment was 37⁺² weeks. The prevalence of SRM was 42% (59/139) with AmnioSense™ giving a sensitivity of 98% (58/59) and specificity of 65% (52/80). Conclusions: Thirty-eight percent (53/139 women) with SRM would have been correctly identified as having intact membranes without the need for a speculum examination. Twenty-five percent of AmnioSense™ false-positive results were associated with positive high vaginal swab results (7/28). These data suggest that a negative AmnioSense™ result can provide reassurance of intact membranes. Use of the AmnioSense™ test before considering speculum examination could reduce the number of speculum examinations undertaken, with benefit to women and concomitant health resource savings.