RESUMO
BACKGROUND: An accurate diagnosis of rupture of membranes is critical to the rendering of appropriate maternity care in both preterm and term patients. Immunoassays, such as the one detecting placental alpha microglobulin-1 (AmniSure) in cervicovaginal secretions, have replaced the traditional speculum-based assessment in some clinical settings; however, the Food and Drug Administration recently issued a warning regarding the potential risks of using the test in isolation. OBJECTIVE: The study aimed to report the performance of AmniSure as a first-line nurse-administered screening test for rupture of membranes in our teaching county hospital obstetrical triage unit and as part of a clinical protocol to diagnose rupture of membranes. STUDY DESIGN: We conducted a retrospective secondary analysis of 310 randomly selected term and preterm patients with concern for rupture of membranes screened with the AmniSure test. We systematically reviewed medical records to determine membrane status at the time of the AmniSure test. We calculated test characteristics of the AmniSure test used independently and in conjunction with speculum-based assessment. RESULTS: Of 302 women evaluated for retrospective determination of membrane status at 17 to 41 weeks' gestation (median, 36.6 weeks' gestation), 208 (68.9%) were intact and 94 (31.1%) were ruptured at the time of the AmniSure test using a gold standard of retrospective membrane status determined by medical record review. A total of 4 false-negative AmniSure results and 16 false-positive AmniSure results were identified. The AmniSure test used independently had a sensitivity of 95.7%, specificity of 92.3%, positive predictive value of 84.9%, and negative predictive value of 98.0%. A rupture of membranes protocol combining AmniSure and clinical assessment had a sensitivity of 98.2%, specificity of 99.5%, positive predictive value of 100.0%, and negative predictive value of 100.0%. CONCLUSION: The AmniSure has a high sensitivity as a first-line nurse-administered screening test for membrane rupture. Consistent with the Food and Drug Administration warning, the sensitivity, specificity, positive predictive value, and negative predictive value are improved when it is used as part of a clinical protocol and not in isolation. Determination of membrane status remains challenging in a small subset of patients, especially those with an equivocal speculum-based assessment; therefore, engaging women in their care and careful follow-up for identifying persistent or recurrent symptoms are required.