A Comparison of Rapid Immunoassay Tests for the Detection of Ruptured Membranes

Premature rupture of membranes (PROM) is defined as spontaneous rupture of membranes (ROM) before the onset of uterine contractions. Its diagnosis is often obvious with the woman presenting with leakage of amniotic fluid, but it could also turn out to be a difficult diagnostic dilemma.

The diagnosis of fetal membrane rupture is conventionally made using a clinical assessment. First, by speculum examination, the clinician looks for amniotic fluid leaking from the cervical os. If clear fluid is visualized leaking from the cervical os, the diagnosis is positive for fetal membrane rupture. More commonly, leaking is absent, and a more extensive workup is required, which includes nitrazine/pH testing, visual inspection of pooling of fluid in the posterior fornix, and a microscopic evaluation of the collected specimen (ferning). Although this approach is considered the standard of care, it is fraught with inaccuracies, requires an intrusive examination and may not provide a rapid diagnosis.

Rapid, point of care, qualitative immunochromatographic tests (ie., Amnisure®, ActimProm®, Amnioquick® Complete and ROM Plus®) that detect proteins found in amniotic fluid at high concentrations, have been used to diagnose the rupture of membranes (ROM) for several years. In many hospitals, Amnisure® has replaced the sterile speculum exam as the standard of care for diagnosing ROM. It identifies Placental Alpha Microglobulin-1 (PAMG-1), a 34 kd fetal glycoprotein, in cervicovaginal secretions.

ROM Plus® ActimProm®and Amnioquick® Complete+ are newer additions into the market for testing for PROM. Both these tests use a monoclonal/polyclonal antibody approach to detect two different proteins found in amniotic fluid at high concentrations. They detect Placental Protein-12 (also known as Insulin-like Growth Factor Binding Protein-1 - IGFBP-1) as well as Alpha Fetoprotein (AFP).

The aim of the study is to demonstrate substantial equivalence of IGFBP-1/AFP tests with the "predicate device" Amnisure®. Stated in statistical terms, the aim is to demonstrated that IGFBP-1/AFP tests are non-inferior to Amnisure® in terms of sensitivity and specificity when both are compared in a paired-sample fashion to a common referent standard (gold standard), which is clinical assessment.