Paper-Based Congo Red Tests Show Promise for Predicting Preeclampsia: Research Shows
Preeclampsia (PE) is a serious pregnancy complication characterized by new-onset hypertension with proteinuria and is a major cause of maternal and perinatal mortality. Current diagnostic methods are inadequate for early prediction, and biomarker-based research aims to improve early detection of PE.
Congo red–based tests are simple, affordable, and suitable for resource-limited settings. This study aimed to evaluate and compare the efficacy of the paper-based Congo red diffusion (PCD) test and the nitrocellulose membrane-based Congo red dot (NC-CRD) test in predicting pre-eclampsia (PE). The presence of urinary misfolded proteins was assessed by two different CR-based methods - a paper based Congored diffusion test using whatman filter paper, and a standard nitrocellulose membrane using Congo red dye. Both methods were evaluated and compared for their efficiency, specificity, sensitivity and accuracy.
PCD test showed significantly higher positivity and CR diffusion zone area (P<0.001), with 163.7±23 mm² (positive) and 59.73±12.98 mm² (negative). Sensitivity and specificity were 84.09% and 80.36% for PCD, and slightly higher for NC-CRD at 88.64% and 82.14% (P<0.001). Accuracy was 82% for PCD and 85% for NC-CRD, with no significant difference between methods (P=0.44). ROC analysis showed AUC of 0.90 (PCD) and 0.93 (NC- CRD), indicating slightly better performance of NC-CRD. PCD is simple with visual interpretation, while NC-CRD is more standardized with clearer results, improving accuracy.
The PCD test is relatively simple and does not require any specialized equipment or extensive training. However, the interpretation of results can be subjective as it involves visual assessment of diffusion zone along with Congo red dye. The NC-CRD test also benefits from a more standardized procedure and clearer result interpretation with enhancing the accuracy.
PE is a multi-organ unpredictable disorder leading to a variety of clinical phenotypes, symptoms and outcomes. At present, there is an elevated blood pressure, proteinuria, pedal edema, visual disturbance, which were the indicators for diagnosing PE but these symptoms are not specific to consider the management of therapeutic intervention. In diagnosing, point-of-care devices are generally advantageous compared with current laboratory assays due to cost effectiveness, screening time consumption, fewer requirements of a skilled technician as well as an instrument. Time is a crucial factor in the management of pre-eclampsia as timely diagnosis can significantly impact maternal and fetal outcomes. The PCD test typically provides results within 3-5 minutes making it a viable option for rapid screening at point of care. Cost of test is another essential consideration particularly in low-resource settings where healthcare budgets are constrained. The materials required for PCD test are generally less expensive than those for the NC-CRD test however the slight increase in cost for the NC- CRD test may be justified by its higher sensitivity and specificity. The high sensitivity and specificity of both tests exhibited their potential valuable tools in the early prediction of PE and choice between the PCD and NC-CRD tests may ultimately depend on the specific clinical context including the need for rapid results, availability of resources and the level of training of healthcare personnel. For widespread implementation especially in rural and under-resourced areas, the simplicity and low cost of the PCD test might make it more accessible.
In conclusion, both the PCD and NC-CRD tests showed promising potential for the early prediction of PE. The PCD test offers a cost-effective, less turnaround time, ease to use, low technology and simple option at point of care, while the NC-CRD test provides slightly higher specificity, sensitivity towards the disease condition, accuracy and reliable results. The choice of test should be tailored to the specific needs and resources of the healthcare setting with a focus on maximizing diagnostic accuracy and improving maternal and fetal outcomes. Further research and refinement of these tests will continue to enhance their utility in clinical practice.
Source: Prabhu M R et al. / Indian Journal of Obstetrics and Gynecology Research 2026;13(2):269–275
