Clinical performance of
sFlt
‐1/
PlGF
ratio triage in suspected pre‐eclampsia: A prospective, observational multicenter diagnostic‐triage study in S
Ismail Bhorat, Priya Soma‐Pillay, Lawrence Chauke, Mushi Matjila, Tshidi Sebitloane, Nitalia Naidoo, Manu Vatish Abstract
Objective
To evaluate the diagnostic and short‐term predictive performance of the soluble fms‐like tyrosine kinase‐1/placental growth factor (sFlt‐1/PlGF ratio) in South African women with suspected pre‐eclampsia (PE), comparing thresholds of ≥ 33 and ≥ 38 in a predominantly African population.
Methods
This was a prospective, observational diagnostic‐triage multicenter study across four tertiary hospitals in South Africa. A total of 555 women with suspected PE with complete outcome data were enrolled from four study sites. The sFlt‐1/PlGF ratio (Elecsys, Roche Diagnostics) was measured at presentation and comprehensive clinical and delivery outcome data were collected. Diagnostic and short‐term predictive performance for sFlt‐1/PlGF thresholds (≥ 33 and ≥ 38) were assessed using sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), receiver operating characteristics (ROC) and associated area under the curve (AUC).
Results
PE was diagnosed in 349/555 women (62.9%). The sFlt‐1/PlGF ratio showed moderate discrimination for PE (area under the receiver operating characteristic curve [AUROC] 0.78, 95% confidence interval [CI]: 0.7–0.8) overall. Continuous‐data ROC analysis in 418 women from Durban, Johannesburg and Pretoria yielded an AUROC of 0.8465 (95% CI: 0.8090–0.8841). In the all‐site analysis, sensitivity, specificity, PPV, NPV and accuracy were 67.05%, 89.32%, 91.41%, 61.54% and 75.32% at ≥ 33, and 62.46%, 90.29%, 91.60%, 58.68% and 72.79% at ≥ 38, respectively. In short‐term prediction, both thresholds showed high sensitivity (86.5%) for PE within 7 days while specificity/PPV were 77.3%/81.8% at ≥ 33 and 81.8%/84.9% at ≥ 38, with NPVs of 82.9% and 83.7%, respectively. By 28 days, NPVs declined to 62% and 64%.
Conclusion
The sFlt‐1/PlGF ratio is a clinically useful biomarker primarily as a rule‐in triage tool for suspected PE in South Africa. The ratio showed high specificity and PPV in this predominantly African cohort. The exploratory ≥ 33 threshold increased sensitivity relative to ≥ 38, with a small reduction in specificity in the all‐site estimates. The findings support its evaluation as an adjunct to clinical assessment in women with suspected PE. Both thresholds showed limited rule‐out performance beyond short follow‐up supporting the need for reassessment and repeat testing where clinically indicated. These findings support consideration of region‐adapted thresholds and highlight the value of biomarker‐guided triage in African settings.