Intermanufacturer assessment of diagnostic performance of angiogenic ratio vs glycosylated fibronectin in women with suspected pre‐eclampsia

OBJECTIVE: To compare the diagnostic performance of different manufacturers' immunoassays for the soluble fms-like tyrosine kinase-1 (sFlt-1)-to-placental growth factor (PlGF) ratio with that of a point-of-care (PoC) test for glycosylated fibronectin (GlyFn) in women with suspected pre-eclampsia (PE). METHODS: This was a prospective, single-center, double-blinded, non-interventional study of East Asian women with a singleton pregnancy who presented with hypertension with or without clinical features of PE after 20 weeks' gestation between January 2020 and March 2022. Maternal serum samples were collected at the time of presentation, and subsequent management followed the departmental protocol, based on gestational age, severity of hypertension, fetal condition and presence of severe PE features. Women diagnosed with PE at presentation were excluded. PE was diagnosed according to the 2018 International Society for the Study of Hypertension in Pregnancy classification. Levels of sFlt-1 and PlGF were measured using the Cobas e411 (Roche Diagnostics), BRAHMS KRYPTOR (ThermoFisher Scientific) and iMAGIN 1800 (Ningbo Aucheer) platforms. GlyFn levels were measured using the Lumella™ GlyFn PoC test (DiabetOmics Inc.). The predictive performance of each test to rule out PE within 7 days and rule in PE within 28 days from the date of presentation was assessed. Based on the PROGNOSIS study, a sFlt-1/PlGF ratio of ≤ 38 on the Roche platform was used to predict the absence of PE within 7 days. The sFlt-1/PlGF ratio was classified as high or low using platform-specific thresholds equivalent to a Roche sFlt-1/PlGF ratio of 38, which were derived using Passing-Bablok regression. GlyFn was categorized as high or low using two reported clinical management thresholds (263 μg/mL and 510 μg/mL). RESULTS: Overall, 236 women with suspected PE were included, of whom 70 (29.7%) were diagnosed with PE; 36 (51.4%) and 70 (100%) developed PE within 7 days and 28 days, respectively. Eighty-eight (37.3%) women had a sFlt-1/PlGF ratio of > 38 on the Roche platform, 79 (33.5%) women had a sFlt-1/PlGF ratio of > 55 on the KRYPTOR platform and 96 (40.7%) women had a sFlt-1/PlGF ratio of > 40 on the iMAGIN 1800 platform. Furthermore, 62 (26.3%) and four (1.7%) women had a GlyFn level of > 263 μg/mL and > 510 μg/mL, respectively. The negative predictive value (NPV) of the sFlt-1/PlGF ratio measured on the Roche, KRYPTOR and iMAGIN 1800 platforms to rule out PE within 7 days after presentation was 83.3%, 82.0% and 82.9%, respectively, while that for GlyFn > 263 μg/mL and > 510 μg/mL was 82.6% and 70.4%, respectively. The corresponding positive predictive values (PPV) to rule in PE within 28 days after presentation were 50.5%, 52.3% and 46.7%, respectively, for the sFlt-1/PlGF ratio, and 35.4% and 50.0%, respectively, for GlyFn > 263 μg/mL and > 510 μg/mL. CONCLUSIONS: The predictive performance of different manufacturers' assays for the sFlt-1/PlGF ratio to rule in and rule out PE were similar once standardized to a common threshold. Our findings suggest that the sFlt-1/PlGF ratio and GlyFn using a cut-off of 263 μg/mL can both be utilized to rule out PE within 7 days after assessment, with a moderate NPV. The PPV for ruling in PE within 28 days remains poor. © 2024 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.