Evaluation of a new and automated electrochemiluminescence immunoassay for plasma sFlt-1 and PlGF levels in women with preeclampsia

Abstract

The first commercial automated immunoassays specific for soluble fms-like tyrosine kinase 1 (sFlt-1) and placental growth factor (PlGF) (Elecsys sFlt-1 and Elecsys PlGF, respectively) have recently been introduced. We constructed reference range values of plasma levels of sFlt-1 and PlGF, and the sFlt-1/PlGF ratio using Elecsys sFlt-1 and Elecsys PlGF during the second half of pregnancy and evaluated their sensitivity and specificity for the diagnosis of preeclampsia. Plasma samples were collected from 144 normal pregnant women at 19-25, 27-31 and 34-38 weeks of gestation and from 34 women with preeclampsia. The most appropriate reference range curves for plasma levels of sFlt-1 and PlGF, and the sFlt-1/PlGF ratio are presented as quadratic curves after logarithmic transformation. The sFlt-1/PlGF ratio showed the best diagnostic power for both early-onset and late-onset preeclampsia. In addition, a cutoff value of 45 for the sFlt-1/PlGF ratio resulted in the best sensitivity and specificity for the diagnosis of all preeclampsia (97 and 95%, respectively), and for the diagnosis of early-onset preeclampsia (100 and 95%, respectively). Using another 50 pairs of serum and plasma samples, including those from normal pregnant women and preeclamptic women, the plasma recovery rates of sFlt-1 and PlGF were 0.89 and 0.85, respectively; the correlation determinations between serum and plasma samples were 0.999 for sFlt-1, 0.990 for PlGF and 0.987 for sFlt-1/PlGF ratio. In conclusion, measurement of the plasma sFlt-1/PlGF ratio determined by Elecsys sFlt-1 and Elecsys PlGF and using a cutoff value of 45 might assist in the diagnosis of preeclampsia, especially for early-onset preeclampsia.