sFlt-1 and soluble endoglin concentrations in serum vs plasma in preterm preeclampsia: Are they interchangeable for biomarker studies?

Soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sENG) are increased in the circulation of women with preeclampsia. We examined whether they differ in concentration between plasma and serum samples. Maternal blood was collected and processed for serum and plasma, from 28 women with preterm preeclampsia and 18 gestation matched controls (<34 weeks). Significantly higher sFlt-1 was detected in preeclamptic serum compared to plasma. Significantly higher levels of sENG were identified in serum compared to plasma from control pregnancies. Thus these data show the sample type (serum or plasma) needs to be consistent within comparisons for both sFlt-1 and sENG.