Prediction of microbial invasion of the amniotic cavity in women with preterm labour: analysis of multiple proteins in amniotic and cervical fluids

Objective: Microbial invasion of the amniotic cavity is a major cause of preterm delivery and the diagnosis is dependent on invasive amniocentesis. The objective was to determine whether specific proteins in amniotic and cervical fluids alone, or in combination, could identify bacterial invasion.

Design: A prospective follow-up study.

Population: Women with singleton pregnancies presenting with preterm labour between 22 and 33 weeks of gestation (n = 89).

Setting: Sahlgrenska University Hospital, Gothenburg, Sweden.

Methods: Amniotic and cervical fluid was analysed with polymerase chain reaction for Mycoplasmas, and was cultured for aerobic and anaerobic bacteria. Twenty-seven proteins were analysed using multiplex technology. Individual levels of each protein were compared in order to find associations between different proteins and microbial invasion of the amniotic cavity. Predictive models based on multiple proteins were created using stepwise binary logistic regression.

Main outcome measure: The main outcome measure was microbial invasion of the amniotic cavity.

Results: Microbial invasion of the amniotic cavity was present in 17% (15/89) of the women. Concentration levels of several amniotic and cervical proteins were significantly higher in women with microbial invasion of the amniotic cavity. Three multivariate predictive models were found. The predictive power of the non-invasive model (73% sensitivity, 88% specificity, 55% positive predictive value, 94% negative predictive value) was as good as the invasive models. Area under the receiver operating characteristic (ROC) curve and likelihood ratio were 0.87 and 6.0, respectively.

Conclusions: Prediction of intra-amniotic infection using selected cervical proteins was equally good as prediction using the same proteins collected from amniotic fluid, or a combination of cervical and amniotic proteins.