Complete Blood Count Predicts Asymptomatic Preterm Birth

Preterm birth (PTB), defined as birth before 37 complete weeks of gestation, is a very serious obstetric problem worldwide. It affects 5% to 18% of all deliveries in the world and represents an enormous health care burden.

One of the most simple, economic, and routine clinical tests during pregnancy is the complete blood count (CBC). CBC and its derived parameters, including neutrophil‐to‐lymphocyte ratio (NLR) and platelet‐to‐lymphocyte ratio (PLR), have been recognized as inflammatory markers for low‐grade inflammatory diseases in recent years.

Medical Laboratory Scientists at the Fujian Medical University (Fuzhou, China) and their colleagues included in a retrospective case‐control study, 15,387 total pregnant women for preterm deliveries and term deliveries between January and December 2017. After adjusting for these four clinical features with propensity score‐matched (PSM) analysis, a total of 105 and 210 pregnant women were retained in the study group and control group, respectively.

A Sysmex blood cell counter (Kobe, Japan) was used as a blood cell counting machine. The CBC parameters used in the study were as follows: WBC, white blood cell; Neu#, neutrophil count; Lym#, lymphocyte count; Mon#, monocyte count; HGB, hemoglobin; HCT, hematocrit; RDW, red cell distribution width; PLT, platelet count; MPV, mean platelet volume; PCT, plateletcrit; PDW, platelet distribution width; NLR, neutrophil‐to‐lymphocyte ratio; LMR, lymphocyte‐to‐monocyte ratio; PLR, platelet‐to‐lymphocyte ratio.

The team reported that NLR, MLR, PLR, PDW, and lymphocytes were statistically different between the two groups before PSM analysis. After PSM analysis, the statistical differences between the first four indicators (NLR, MLR, PLR, and PDW) were even more statistically significant, in addition, HGB and MPV, HCT also reached statistical differences between the two groups after PSM analysis. The mean values of NLR, PDW, MPV, HGB, HCT, PLR were significantly higher, and LMR and lymphocytes were significantly lower in preterm delivery group after PSM analysis.

The authors concluded that the combined marker of CBC parameters can supplement other markers to predict PTB about 10 weeks in advance. This combined marker had a very high negative predictive value for PTB. Therefore, in subjects with normal combined marker value, further screening tests for PTB may be eliminated unless clinical suspicion is high. The study was published on march 27, 2020 in the Journal of Clinical Laboratory Analysis.

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Fujian Medical University
Sysmex