Multicenter evaluation of the first automated Elecsys sFlt-1 and PlGF assays in normal pregnancies and preeclampsia
Objectives: Performance evaluation of Elecsys® sFlt-1 and PlGF assays. Design and methods: Within-, between-run, total imprecision, functional sensitivity, inter-laboratory comparison, method comparison and lot-to-lot reproducibility were evaluated. Results: Within- and between-run CVs were below 4% for sFlt-1 >60 and PlGF >20. pg/mL. Total imprecision CVs were below 4.3%. Functional sensitivity was <5. pg/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 (1107. pg/mL) and second trimesters (1437. pg/mL) but increased in the third trimester (2395. pg/mL), while median PlGF levels increased in the first (30. pg/mL) and second trimesters (279. pg/mL) and peaked at 29 to 32. weeks (626. pg/mL) and decreased thereafter (340. pg/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 (6894-34,624. pg/mL), whereas PlGF levels were lower (9.2-80. pg/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). Conclusion: 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.