Elecsys sFlt-1 and Elecsys PlGF

The Elecsys sFlt-1 and Elecsys PlGF are immunoassays that quantitatively measure soluble fms-like tyrosine kinase-1 and placental growth factor in human serum. The sFlt-1/PlGF ratio is used as an aid in risk assessment for pregnant women (23+0 to 34+6/7 weeks gestation) hospitalized with hypertensive disorders of pregnancy to predict development of preeclampsia with severe features within two weeks, and must be used with clinical assessment and routine laboratory testing.

The candidate device uses electrochemiluminescence (ECLIA) detection on cobas e analyzers with an 18-minute assay time, while the predicate uses Time-Resolved Amplified Cryptate Emission (TRACE) technology on B·R·A·H·M·S KRYPTOR analyzers with a 9-minute assay time. The candidate accepts human serum only (versus serum/plasma for predicate), uses phosphate buffer in reagents (versus bovine albumin), employs 2-point calibration (same as predicate), and has broader measuring ranges: sFlt-1 80–85,000 pg/mL and PlGF 10–5,400 pg/mL. Both use sandwich immunoassay methodology and the same calibration approach.

CLSI guideline EP05-A3 for precision (repeatability and intermediate precision); CLSI EP06-Ed2 Study Design B for linearity; CLSI EP17-A2 for limit of blank, limit of detection, and limit of quantitation. No ISO, IEC, or ASTM standards are explicitly cited.

Both devices measure the same analytes (sFlt-1 and PlGF ratio) with identical intended use for preeclampsia risk assessment in the same patient population (23+0 to 34+6/7 weeks gestation, hospitalized with hypertensive disorders). Although detection methods differ (ECLIA versus TRACE), both employ sandwich immunoassay principles with monoclonal antibodies and achieve comparable analytical performance: sensitivity 91.4%, specificity 77.3%, NPV 94.7%, PPV 66.9% at cutoff 38 in the clinical study. Non-clinical performance (precision, linearity, analytical sensitivity, specificity, interference testing) meets predefined acceptance criteria across multiple reagent lots. The clinical PRAECIS study validates the sFlt-1/PlGF ratio cutoff of 38 in the intended population, demonstrating substantially equivalent prognostic performance for predicting severe preeclampsia within two weeks.