The Clinical Utility of the Congo-Red Dot Test for Diagnosis and Early Prediction of Preeclampsia During Pregnancy

Preeclampsia is a pregnancy-specific hypertensive disorder and a leading cause of maternal and perinatal morbidity and death worldwide. When left untreated, preeclampsia leads to seizures (eclampsia), stroke, hemorrhage, kidney and liver failure, and death. The World Health Organization (WHO) estimates that 99% of preeclampsia-related deaths occur in low- and mid-income countries. Although most cases of maternal death are preventable, it is estimated that ~63,000 women die annually due to preeclampsia alone.

In developed countries, such as the U.S. and UK, development and implementation of clinical guidelines for diagnosis and management of preeclampsia has resulted in a dramatic decrease in maternal morbidity and mortality. Some of these measures include: a) blood pressure and dipstick proteinuria screening during each prenatal visits; b) extensive laboratory work-up to rule-out hemolysis, elevated liver enzymes, and thrombocytopenia (HELLP) syndrome; c) hospital admission for intensive clinical observation; d) use of magnesium sulfate and anti-hypertensive medication to prevent eclampsia and intracranial hemorrhage and e) medically indicated early delivery for strict clinical criteria of severity given that delivery is the only definitive cure for preeclampsia.

It is well-recognized that the number of medically-indicated early deliveries in the U.S. and U.K. exceeds those necessary to prevent maternal death or morbidity related to preeclampsia. However, in the era of widespread use of antenatal corticosteroids and advances in neonatal intensive care, in developed countries, obstetricians lean more towards indicating delivery than they were three decades ago. At present in the U.S., preeclampsia is estimated to trigger 70% of medically indicated preterm births. Yet, implementation of the same guidelines is not feasible for low- or mid-income countries. In this scenario, the tendency is to prolong pregnancy at least until 34 weeks so that the likelihood of survival for the premature neonate is maximized. Recognizing this conundrum, increased emphasis has been placed on finding novel diagnostic and prognostic biomarkers that may help with identification of preeclamptic women in real need of medically-indicated deliveries as opposed to those whose pregnancy could be safely extended. That said, for low- and mid-income countries, such biomarkers have the potential to significantly help with current barriers in reducing maternal morbidity and deaths from severe preeclampsia. Because compliance with physician referral and transport to the hospital are significant issues in rural areas, the earlier the problem is identified, the better the outcome. Accurate identification of women whose pregnancies are at high risk for preeclampsia or eclampsia would result in timely referral to medical facilities where appropriate treatments (i.e magnesium sulfate or medically-indicated delivery) can be provided. Additionally, an accurate diagnostic test for preeclampsia implemented in a developing country will allow maternity units to run more cost effectively by avoiding unnecessary referrals, unnecessary admissions for 24h protein assessment. This will also reduce the number of admissions for labor induction, the number of inductions in general and indirectly the number of C-sections.

Traditionally, the diagnosis of preeclampsia relies on presence of hypertension and proteinuria. Unfortunately, these signs are often non-specific and could be confounded by many co-morbidities including essential hypertension and chronic kidney disease. Spearheaded by proteomics research, our group identified that women with severe forms of preeclampsia excrete in their urine high amounts of unfolded or misfolded proteins. This phenomenon classifies preeclampsia as a protein conformational disorder similar to Alzheimer's and prion disease, yet particular to pregnancy. It logically followed that misfolded proteins in preeclampsia urine should exhibit congophilia (affinity for the azo-dye Congo Red). Congo Red was developed for textile industry in the 1800', but later found to have self-assembling properties and to selectively stain misfolded amyloid in brains of patients with Alzheimer's. Based on these premises, a simple urine diagnostic test [Congo Red Dot (CRD) Test] has been designed, developed and validated in our research laboratory.