Analytical Performance and Quality Indicators of Fully Automated Immunoassays for sFlt-1 and PIGF

Background: The ratio of the antiangiogenic factor, soluble fms-like tyrosine kinase 1 (sFlt-1), to the proangiogenic factor, placental growth factor (PIGF), is associated with increased risk of preeclampsia. Here, we describe an analytical evaluation of the Elecsys sFlt-1 and PIGF assays at the first North American site in which they were clinically implemented. Methods: The analytical evaluation included short- and long-term imprecision, method comparison, accuracy, linearity, sample stability, limit of quantification verification, and measurement uncertainty. Quality indicators were also evaluated, including turnaround time and repeat test frequency. Results: Short-term (13-day) and long-term (12-month) imprecision for sFlt-1 and PIGF were <4% CV. Method comparison (n = 40) between Roche cobas e602 and e411 exhibited r > 0.99 and bias <10%. sFlt-1/PIGF ratio ruleout cutoffs (<33 and <38) and rule-in cutoffs (>38, >85, and >110) exhibited negative percent agreement and positive percent agreement of 100%, respectively (n = 40). During the first 12 months, 257 orders were placed, repeat test frequency was 17.5%, mean time between repeat orders was 23 days, and 72.0% of results were reported within 2 h from sample receipt when quality control was run continuously. Conclusions: We describe analytical performance parameters and quality indicators of the Elecsys sFlt-1 and PIGF assays, which was the first North American clinical laboratory site to implement these assays in support of the institution's high-risk obstetrical unit.

Automated summary

This study evaluated the analytical performance and quality indicators of the Elecsys sFlt-1 and PIGF assays at the first North American site to implement them clinically. Results showed low short-term and long-term imprecision, accurate method comparison, and compliance with repeat test frequency and turnaround time requirements.