P 22 Analytical evaluation of soluble fms-like tyrosine kinase 1 (sFlt-1) and placental growth factor (PlGF) on Brahms Kryptor automated immunoassay for the diagnosis of preeclampsia

Abstract

Background Preeclampsia is one of the leading hypertensive disorders in pregnant women worldwide and is characterized by maternal vascular dysfunction. Current diagnosis of preeclampsia in the U.S. is based on non-specific tests such as new onset of hypertension and proteinuria after 20 weeks of gestation. More recently, two emerging biomarkers anti-angiogenic factor soluble fms-like tyrosine kinase 1 (sFlt-1) and pro-angiogenic factor placental growth factor (PlGF), have been demonstrated to be involved in the pathophysiology of preeclampsia. Studies have shown that the usefulness of sFlt-1/PlGF ratio in confirming or ruling out suspected preeclampsia cases. Thus, wider availability of the automated measurement of sFlt-1 and PlGF has the potential of improving the clinical management of preeclampsia. Methods This study examined K2-EDTA plasma samples from 50 patients on Brahms Kryptor, an automated immunoassay platform. QC materials were used to access intra- and inter-precision of the assay. Lower limit of quantitation and interference studies were determined using pooled patient plasma. Results The sFlt-1 and PlGF assays demonstrated an analytical measuring range of 90–69,000 pg/mL and 11–7000 pg/mL, respectively (r2 > 0.99). Lower limit of quantitation (20% CV) was interpolated to be 35 pg/mL for sFlt-1 and 10 pg/mL for PlGF. Total precision for both assay displayed CVs of y = 0.9939x-37.15 with an overall bias of 90.35 for sFlt-1; and y = 0.8936x + 2.562, with an overall bias of −39.644 for PlGF. The larger differences in overall bias based on individual tests however was greatly improved when a ratio of sFlt-1/PlGF is taken into account for method comparison, yielding an equation of y = 1.05x + 0.02, with an overall bias of 0.84. Conclusion The pre-eclamptic biomarkers, sFlt-1 and PlGF assayed on the Brahms Kryptor platform, demonstrate good analytical performance and are acceptable for clinical studies defining the role of these biomarkers for preeclampsia.