Performance evaluation of Elecsys® sFlt-1 and PlGF assays.

Within-, between-run, total imprecision, functional sensitivity, inter-laboratory comparison, method comparison and lot-to-lot reproducibility were evaluated.

Within- and between-run CVs were below 4% for sFlt-1 >60 and PlGF >20pg/mL. Total imprecision CVs were below 4.3%. Functional sensitivity was <5pg/mL. Inter-laboratory CVs were <5%. Elecsys correlated well with Quantikine VEGF-R1 (r=0.960) and PlGF (r=0.968). Lot-to-lot comparisons yielded highly correlated results (r>0.999). In healthy pregnancies, the median levels of sFlt-1 remained constant in first (1107pg/mL) and second trimesters (1437pg/mL) but increased in the third trimester (2395pg/mL), while median PlGF levels increased in the first (30pg/mL) and second trimesters (279pg/mL) and peaked at 29 to 32weeks (626pg/mL) and decreased thereafter (340pg/mL). The sFlt-1/PlGF ratio is highest in the first trimester (median: 28) but remained constant in the second (median: 4.7) and third trimesters (median: 5.1). In PE/HELPP samples matched for gestational age the sFlt-1 levels were significantly higher (6894–34,624pg/mL), whereas PlGF levels were lower (9.2–80pg/mL) and the median sFlt-1/PlGF ratio is much higher (461; range: 121–2614) than in apparently healthy pregnancies (3.6; range: 0.3–105).

The new Roche Elecsys sFlt-1 and PlGF immunoassay showed excellent precision and reliability. There was a clear difference in the Elecsys sFlt-1/PlGF ratio between samples obtained from women with apparently normal pregnancy at the time of blood collection and those diagnosed with PE/HELLP at the same age of gestation.