C-reactive protein concentration in vaginal fluid as a marker for intra-amniotic inflammation/infection in preterm premature rupture of membranes.

OBJECTIVE

The purpose of this study was to determine whether C-reactive protein (CRP) concentrations in vaginal fluid can identify patients with intra-amniotic inflammation/infection (IAI) and predict adverse outcome in preterm premature rupture of membranes (PROM).

METHODS

The study population consisted of 121 singleton pregnant women with preterm PROM (36 weeks of gestation) who had an amniocentesis and vaginal fluid collection. A Dacron polyester-tipped applicator was soaked with vaginal fluid for 10 seconds and diluted with 1 mL buffer solution. Amniotic fluid was cultured for aerobic and anaerobic bacteria, as well as mycoplasmas. Vaginal fluid CRP and amniotic fluid matrix metalloproteinase-8 (MMP-8) were determined by specific immunoassays. IAI was defined as an amniotic fluid MMP-8 concentration >23 ng/mL and/or a positive amniotic fluid culture. Nonparametric tests and survival techniques were used for statistical analysis.

RESULTS

Patients with IAI had a significantly higher median vaginal fluid CRP concentration than those without IAI (median (range), 7.8 (0.1-1310.1) ng/mL vs. 1.0 (0.1-319.4) ng/mL, p < 0.005). The median amniotic fluid white blood cell (WBC) count was significantly higher in patients with a vaginal fluid CRP concentration of >10 ng/mL than in those with a lower concentration (median (range), 82.5 (0-8640) cells/mm3 vs. 2 (0->1000) cells/mm3, p < 0.001). Patients with vaginal fluid CRP concentration of >10 ng/mL had a significantly shorter sampling-to-delivery interval and higher rates of preterm delivery within five days, funisitis, and histologic chorioamnionitis than did those with a vaginal fluid CRP concentration below this cut-off. A vaginal fluid CRP cut-off of 10 ng/mL had a specificity of 89% and a sensitivity of 45% in the identification of IAI.

CONCLUSION

An elevated CRP concentration in vaginal fluid collected by polyester-tipped applicator is a risk factor for intra-amniotic inflammation/infection and impending preterm delivery in preterm PROM.