Red cell distribution width and preeclampsia: a systematic review and meta-analysis

Preeclampsia is a serious pregnancy-related disease which may lead to adverse health effects to the mother and fetus. Besides many publications on the association of red cell distribution width (RDW) and preeclampsia, there has been no published meta-analysis. This necessitated the present systemic review and met-analysis to assess the RDW in relation to preeclampsia.

Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline was followed. Relevant published studies were searched in PubMed, Cochrane library, Google scholar, Scopus, Embase and CINAHL using the term "Preeclampsia OR eclampsia AND red cell distribution width OR red blood cells). Modified Newcastle - Ottawa quality assessment scale was used for critical appraisal of retrieved studies. Pooled Meta logistic regression was computed using OpenMeta Analyst software. Subgroup and meta-regression methods were performed to analyse the heterogeneity.

Eleven case control studies were included in the met-analyses with a total of 951 cases (preeclampsia) and 2024 controls. The mean (SD) of the RDW level was significantly higher in women with preeclampsia compared to controls [15.10 (2.48) % vs. 14.26(1.71) %, P < 0.001]. The mean difference was 0.85, 95% CI = 0.26-1.43. Due to a high heterogeneity (I² = 90.45, P < 0.001), the continuous random effect model was used.Eight studies compared RDW level in the mild (N = 360) with severe cases (N = 354) of preeclampsia. The RDW level was significantly higher in women with severe preeclampsia compared to those with mild preeclampsia [15.37 (2.48) % vs. 14.037(1.79) %, P < 0.001]. The mean difference was 1.07, 95% CI = 0.45-1.70. Since there is a high heterogeneity [I² = 76.67, P < 0.001], the continuous random effect model was used.Through the met-regression model, except for the region of the study (P < 0.001), none of investigated variables (age, parity, quality of the study) was significantly associated with the investigated heterogeneity. The outliers (3studies) were removed to reduce the heterogeneity. The pooled meta-analysis of the remaining 8 studies showed a significant difference in the RDW between preeclamptic women compared with the controls. The mean difference was 0.93, 95% CI = 0.56-1.31, P < 0.001. Because of heterogeneity [I² = 69.6, P = 0.002], the continuous random effect model was used.

RDW level was significantly higher in women with preeclampsia compared to controls. Similarly, women with severe preeclampsia had significantly higher RDW than those with the mild form.