The clinical significance of a positive Amnisure test in women with preterm labor and intact membranes

Abstract

Objective: This study was conducted to examine the frequency and clinical significance of a positive Amnisure test in patients with preterm labor and intact membranes by sterile speculum exam.

Study design: A retrospective cohort study was performed including 90 patients with preterm labor and intact membranes who underwent Amnisure tests prior to amniocentesis (< 72 h); most patients (n=64) also underwent fetal fibronectin (fFN) tests. Amniotic fluid (AF) was cultured for aerobic/anaerobic bacteria and genital mycoplasmas and assayed for matrix metalloproteinase-8.

Results: (1) the prevalence of a positive Amnisure test was 19% (17/90); (2) patients with a positive Amnisure test had significantly higher rates of adverse pregnancy and neonatal outcomes (e.g., impending preterm delivery, intra-amniotic infection/inflammation, and neonatal morbidity) than those with a negative Amnisure test; (3) a positive test was associated with significantly increased risk of intra-amniotic infection and/or inflammation, delivery within 7, 14, or 28 days and spontaneous preterm birth (< 35 weeks) among patients with a negative fFN test.

Conclusions: A positive Amnisure test in patients with preterm labor and intact membranes is a risk factor for adverse pregnancy outcome, particularly in patients with a negative fFN test. A positive Amnisure test in patients without symptoms or signs of ROM should not be taken as an indicator that membranes have ruptured.

Figures

Figure 1

Amniotic fluid MMP-8 concentrations according to the presence or absence of clinical evidence of ROM and the result of Amnisure test (a negative Amnisure test: median, 1.2 ng/mL [range, 0.3–2109.1 ng/mL]; a positive Amnisure test: median, 49.3 ng/mL [range, 0.3–5304.8 ng/mL])

Figure 2

Kaplan-Meier Survival Distribution Function by Test Result [The median test-to-delivery duration and hazard ratio (95% confidence interval) for each group adjusted for gestational age at test, cervical dilatation, and intra-amniotic infection and/or inflammation are as follows: Amnisure (+) fFN (+): 9.7 days, 3.8 (1.1–12.8); Amnisure (+) fFN (−): 5.3 days, 5.0 (1.4–18.0); Amnisure (−) fFN (+): 25.7 days, 3.4 (1.3–8.5); Amnisure (−) fFN (−): 53.7 days, 1(reference)]