PGF and preeclampsia: In this study, the sFlt-1/PlGF ratio of ≤38 had an NPV of 98.6% (95% CI, 97.2%–99.4%) for ruling out preeclampsia within 1 week.31 An sFlt-1/PlGF ratio ≤38 at 36 weeks’ gestation was also clinically useful for ruling out severe preeclampsia among low-risk patients in an unselected cohort of nulliparous women (NPV, 99.2%).27 Sabrià et al28 showed that between 24 and 34 weeks’ gestation, no subsequent determination was needed to completely rule out early-onset preeclampsia when the first sFlt-1/PlGF ratio determination was ≤38, in singleton pregnancies with signs or symptoms of this syndrome.