Maternal C-reactive protein for detection of chorioamnionitis: an appraisal.

Premature delivery is still a significant problem in obstetrics, and chorioamnionitis is an unwelcome complication. C-reactive protein (CRP) is a circulating marker of low-grade inflammation and the role of its measurement in clinical practice remains unclear for many conditions. It has been claimed that estimation of CRP is helpful in the diagnosis of chorioamnionitis, and this study aims to appraise such claims. Following review of the literature, six reports were recruited for further metanalysis, including 466 cases. The overall prevalence of chorioamnionitis was 41% (191/466). The overall diagnostic activity showed sensitivity, specificity, false-positives and false-negatives of 72.8%, 76.4%, 23.6% and 27.2%, respectively. Therefore, we can conclude that estimation of maternal CRP is not helpful in the detection of chorioamnionitis, compared with standard investigations.


Introduction
Premature delivery is still a significant problem in obstetrics [1]. It has multiple causes; about 50% of cases are thought to be due to infection. Potential pathogens largely arise from the ascending route and from the endogenous vaginal flora, and may cause chorioamnionitis [1]. The recent increase in knowledge about infection and preterm delivery has engendered many new questions and should make us rethink our long-held beliefs and management strategies [2]. During threatened preterm delivery, general and local infections increase the risks of amniotic infection, premature rupture of membranes (PROM), preterm delivery, and neonatal and/or maternal morbidity of infectious origin [3].
Chorioamnionitis is a totally unwanted complication. Systematic vaginal and blood sampling is helpful in determining the appropriate option in this situation [1][2][3]. The various serologic and amniotic fluid tests that may identify activation of the host immune and inflammatory responses as a consequence of the microbial invasion of the amniotic cavity are very promising, but not yet fully confirmed for clinical use [1][2][3]. Examples of these are Creactive protein (CRP), leukocyte count, vaginal microbiological studies and histological study. These tests may identify the early stages of an infectious process, before the full clinical manifestations of chorioamnionitis.
Here, the author appraises the diagnostic properties of maternal CRP for detection of chorioamnionitis. According to this study, this test has only fair sensitivity and specificity.

Materials and methods
A literature review was performed by means of PubMed (www.pubmed.com) to identify previous reports on the effectiveness of maternal serum CRP measurement compared with standard histological or microbiological methods to detect chorioamnionitis. The operative definition of chorioamnionitis was either histological, which may be asymptomatic, and/ or clinical. The available reports were collected and extracted for the data on the diagnostic properties of serum CRP. The primary data were used for metanalysis. Reports that did not present the diagnostic properties (sensitivity, specificity, false positives and false negatives) were excluded. The overall diagnostic properties (sensitivity, specificity, false positives and false negatives) were then calculated. SPSS 11.0 for Windows was used for statistical analysis.

Discussion
CRP is a circulating marker of low-grade inflammation, thrombosis and vascular injury, and it has been associated with underlying inflammatory processes [10,11]. The role of the measurement of CRP in clinical practice remains unclear for many diseases [10,11], although it has been proposed as helpful in the diagnosis of chorioamnionitis. Among the many previous reports on this topic, some have suggested that CRP has good diagnostic properties [5,8] for the detection of chorioamnionitis, whereas others have found the opposite [4,6,7,9]. The present study revealed a high prevalence of chorioamnionitis among the study population, which underlines the need for an efficient test for the condition. However, in this respect the overall sensitivity and specificity of maternal CRP measurement were only fair, with high false-positive and false-negative rates. We therefore conclude that maternal CRP measurement is not a good tool for the detection of chorioamnionitis, compared with standard tests.