Urinary Congophilia in Pre-Eclampsia: A Potential Diagnostic Biomarker

Pre-eclampsia (PE) causes significant maternal and neonatal morbidity and mortality worldwide, particularly in low- and middle-income countries (LMICs). Current diagnostic methods, such as blood pressure monitoring and proteinuria measurement, have poor sensitivity and specificity. Although biomarkers like PlGF and sFlt-1 improve diagnostic accuracy, their clinical value is limited by cost and infrastructural constraints. The Congo red dot (CRD) test, which identifies misfolded proteins via urinary congophilia, has emerged as a low-cost, noninvasive alternative for detecting PE.

This review evaluated the diagnostic performance of the CRD test by synthesizing evidence from studies across diverse populations, including India, China, and South Africa. Methodologies encompassed prospective cohorts, case-control designs, and meta-analyses, with a focus on sensitivity, specificity, and comparative efficacy against conventional screening tools.

Results indicate that the CRD test achieves high diagnostic accuracy, with reported specificity of 89.2% and sensitivity of 80.2%. The assay provides rapid results (< 3 min) without specialized equipment, demonstrating effectiveness in LMICs. However, performance variability was observed in late-onset PE, and comparative studies yielded conflicting data regarding its superiority over urinary dipstick analysis. Additionally, challenges persist in differentiating PE from other hypertensive disorders with overlapping proteinuria.

The CRD test represents a promising diagnostic tool for PE in LMICS with limited access to advanced diagnostics. Further large-scale validation studies are required to standardize protocols, establish gestational age-specific thresholds, and clarify its role in differentiating PE from confounding conditions. Integration with existing biomarkers may enhance its clinical adoption and diagnostic precision.