The role of eosinophil count and eosinophil-based complete blood cell indices in predicting preeclampsia in the first trimester of pregnancy: a case-control study

Aims: This study aims to investigate the relationship between first-trimester eosinophils and eosinophil-based hematological indices and the development of preeclampsia (PE).Methods: In this retrospective study, 105 pregnant women who underwent a complete blood count between the sixth and fourteenth weeks of pregnancy and were subsequently diagnosed with PE who gave birth at our center were compared with 120 healthy pregnant women. Demographic characteristics, hematological values, eosinophil-based indices and perinatal outcomes were compared between groups. Logistic regression analyses were performed to evaluate factors associated with the development of PE. Additionally, receiver operating characteristic (ROC) analysis was performed to assess the predictive performance of these indices for the development of PE. Results: When comparing the PE group with healthy controls, the median eosinophil count (0.08 vs. 0.10, p=0.013), NER (neutrophil-eosinophil ratio) (76.00 vs. 60.50, p=0.016), LER (leukocyte-eosinophil ratio) (105.43 vs. 91.35, p=0.015), ELR (eosinophil-lymphocyte ratio) (0.04 vs. 0.05, p=0.010) and EBR (Eosinophil-to-basophil ratio) (2.25 vs. 3.00, p=0.002) showed significant differences, but there was no difference in EMR (eosinophil-to-monocyte ratio) (p=0.065). In the multivariable analysis, eosinophil count (adjusted odds ratio [aOR]=0.01, p=0.048), EBR (aOR=0.80, p=0.003), EMR (aOR=0.70, p=0.038), NER (aOR=1.00, p=0.020) and LER (aOR=1.00, p=0.017) were associated with the development of PE. ROC analysis revealed that EBR is the most discriminative eosinophil-based marker (area under the curve [AUC]=0.619). There was no significant difference between the groups with severe and non-severe PE in eosinophil count and eosinophil-based hematological indices (p>0.05). Conclusion: Changes in eosinophil count and eosinophil-based hematological ratios during the first trimester reflect immune system abnormalities that occur prior to the clinical onset of PE. In particular, low eosinophil, EMR with EBR parameters and increased NER with LER values can be considered early indicators of PE risk. These parameters alone have limited predictive performance.