Serum LDH values in hypertensive disorders of pregnancy and their association with maternal and neonatal morbidity: a meta-analysis

Objectives: Serum lactate dehydrogenase has been extensively studied in hypertensive disorders of pregnancy. However, to date, its clinical usefulness in the field remains unknown. The present meta-analysis has been designed to evaluate differences in serum LDH values among patients with hypertensive disorders of pregnancy and to help determine its diagnostic accuracy as well its predictive accuracy in determining adverse pregnancy outcomes. Methods: We searched Medline, Scopus, Clinicaltrials.gov, EMBASE, Cochrane Central Register of Controlled Trials CENTRAL and Google Scholar databases from their inception till March 18, 2021. Meta-analysis was performed using the meta and metafor functions in Rstudio. Pooled mean differences (MD) were calculated with the Hartung-Knapp-Sidik-Jonkman. Meta-regression analyses, publication bias assessment and Trim and Fill function were also performed. The adequacy of the sample size was evaluated with Trial Sequential Analysis. Results: Fifty-two articles were included that comprised 5,340 women with hypertensive disorders of pregnancy and 2,890 healthy controls. The meta-analysis revealed significant differences among patients with preeclampsia (either mild or severe) compared to controls, as well as among patients with mild and severe preeclampsia. Significant asymmetry was noted after examining funnel plots, however, and the trim and fill analysis revealed that differences were significant only among cases with severe preeclampsia and healthy controls. Morbidity outcomes increased with LDH levels > 600 IU/L and particularly when these exceeded 800 IU/L. However, confidence and prediction intervals indicated an underpowered sample size for the accurate determination of the odds of developing maternal morbidity. Conclusions: Despite the extensive research in the field of hypertensive disorders of pregnancy, there is still lack of evidence concerning the diagnostic performance of serum LDH in clinical practice; hence, research should expand in this direction to evaluate its clinical utility.