Discussion
The findings of our meta-analysis suggest that the existing literature supports the existence of significant differences in serum LDH levels among patients with preeclampsia compared to healthy controls. This finding is more predominant in women with severe preeclampsia, compare to those with mild features of the disease. However, at this point it should be noted that these findings are particularly skewed and seem to be attributed to the poor methodological quality of included studies, as well other potential factors (described in the materials and methods), that we could not investigate, due to the lack of substantial differences among the included studies. Of specific importance is the lack of available evidence in the field of the diagnostic accuracy of this biomarker as the vast majority of studies failed to evaluate its sensitivity and specificity. Moreover, we observed a complete lack of data concerning the predictive accuracy of serum LDH on determining adverse maternal and neonatal outcomes in studies enlisted in our systematic review.
However, this does not mean that there is no data to support the potential use of this enzyme in the field of obstetrics as there are scarce data that evaluate its predictive accuracy in the presence of hemolysis. Specifically, the most recent and largest in sample size study in the field suggests that LDH levels >400 IU/L are associated with severe maternal and neonatal complications in the presence of hemolysis [13]. However, a standardized cut-off value has not been established yet as there seem to be large discrepancies among the few studies that exist in the field [24, 25].
Several other diseases may trigger the increase of serum LDH as well, including pregnancy-associated thrombotic thrombocytopenic purpura, diseases of the liver etc [26]. It remains relatively unknown whether increases are comparable, however, current research suggests that the use of combined examinations of LDH with other biomarkers such as liver enzymes may help establish an accurate diagnosis [27].