Congo red test for identification of preeclampsia: Results of a prospective diagnostic case-control study in Bangladesh and Mexico

A point-of-care urine test to predict adverse maternal and neonatal outcomes in Asian women with suspected preeclampsia

OBJECTIVES

To assess clinical utility of the urine Congo red dot test (CRDT) in predicting composite adverse maternal and neonatal outcomes in women with suspected preeclampsia (PE).

METHODS

CRDT result and pregnancy outcomes were prospectively documented in women with new onset or pre-existing hypertension, new or pre-existing proteinuria, PE symptoms and suspected PE-related fetal growth restriction or abnormal Doppler presenting from 20 weeks' gestation between January 2020 and December 2022. Participants and clinicians were blinded to the CRDT result and managed according to internally agreed protocols. Composite maternal outcome was defined as PE, postpartum hemorrhage, intensive care unit admission, and maternal death. Composite neonatal outcome was defined as small for gestational age, preterm birth, 5-min Apgar score < 7, neonatal intensive care unit admission, and neonatal death.

RESULTS

Two hundred and forty-four women out of two hundred and fifty-one (97.2%) had a negative CRDT. All seven women with positive CRDT had both adverse maternal and neonatal outcomes, giving positive predictive values (PPV) of 100%. Rates of composite adverse maternal and neonatal outcomes in CDRT negative women were 103/244 [42.2%, 95% confidence interval (CI) 36.2%-48.5%] and 170/244 (69.7%, 95% CI 63.6%-75.1%), respectively. CRDT negative predictive values (NPV) for adverse maternal and neonatal outcomes were, respectively, 141/244 (57.8%, 95% CI 48.6%-68.2%) and 74/244 (30.3%, 95% CI 23.8%-38.1%).

CONCLUSION

CRDT had low NPV but high PPV for adverse maternal and neonatal outcomes in women with suspected PE. Its role in clinical management and triage of women with suspected PE is limited as it cannot identify those at low risk of developing adverse outcomes.

Comparing urine point-of-care tests to screen preeclampsia: Congo-red dot paper test versus dipstick urinalysis

To compare the urine Congo-red dot paper test (CRD) with dipstick urinalysis to screen preeclampsia (PE). A total of 409 paired spot urine samples were obtained prospectively from women with suspected pre-eclampsia attending for routine hospital visits. Congo-red dot paper test and dipstick urinalysis were examined and compared to screen pre-eclampsia. The agreement between the two urinary test is modest (kappa coefficient = 0.28, 95% CI 0.14-0.42). The specificity of CRD was higher than urinalysis (97.4% vs. 90.4%, p < .001). Urinalysis performed better in sensitivity (77.3% vs. 40.9%, p = .04) and the area under the receiver operating characteristic curves (AUC) (0.84 [95% CI 0.74-0.94] vs. 0.69 [95% CI 0.55-0.83], p = .04) than CRD, respectively. The sensitivity, specificity, AUC of the parallel test of them is 86.4% (64.0%-96.4%), 89.1% (85.5%-92.0%), and 0.88 (95% CI 0.79-0.96). And the serial test is 31.8% (14.7%-54.9%), 98.7% (96.8%-99.5%), 0.65 (95% CI 0.51-0.79), accordingly. The urinalysis is a better diagnosing test for preeclampsia. CRD could aid in the diagnosis of patients with preeclampsia. Combined the two tests in suspected patients may further improve the performance in the diagnosis of preeclampsia. Further study need to be made for its potential clinical practice.

Urine congophilia associated with preeclampsia does not persist 6-months postpartum

INTRODUCTION

Preeclampsia is a common hypertensive disorder of pregnancy. Several studies have demonstrated that protein aggregates, detected through urine congophilia, is associated with preeclampsia; however, it has yet to be investigated whether urine congophilia remains postpartum in these women. In this study, we aimed to augment prior studies and determine whether urine congophilia is present postpartum.

METHODS

Women were recruited from Lyell McEwin Hospital, South Australia. Urine samples were collected during pregnancy and 6-months postpartum from women with non-preeclampsia pregnancies (n = 48) and women with pregnancies complicated by preeclampsia (n = 42). A Congo Red Dot blot test, total protein and creatinine levels from urine, as well as serum Soluble fms-like tyrosine kinase 1 to placental growth factor ratio (sFlt-1:PlGF), were assessed and correlated.

RESULTS

Preeclamptic women exhibited increased urine congophilia (P < 0.01), sFlt-1:PlGF ratio (P < 0.0001) and total protein (P < 0.01) during pregnancy; with a positive correlation between urine congophilia and total protein across the entire cohort (P < 0.0001). Although urine congophilia was no longer detected 6-months postpartum in preeclamptic women, total protein remained elevated (P < 0.05). sFlt-1:PlGF ratio during pregnancy was positively correlated with congophilia across the cohort (P = 0.0007). Serum creatinine was also higher in preeclamptic women during pregnancy (P < 0.001).

DISCUSSION

These results support that urine congophilia is significantly elevated in pregnancies complicated with preeclampsia and show that it does not continue postpartum, although larger cohort studies are needed to determine its feasibility as a diagnostic marker.

CercaTest Red, a novel urine-based point-of-care test for the detection of preeclampsia

OBJECTIVES

Preeclampsia (PE) poses a serious threat to the health of the pregnant woman and her developing fetus due to the difficulty in diagnosing the condition. The disease can develop and worsen suddenly without noticeable signs and symptoms. Thus, there is an urgent need for a simple Point of Care Test (POCT) that improves accessibility to testing and can be used as an aid in the diagnosis of PE. CercaTest Red is a noninvasive detection kit for impending preeclampsia using urine from pregnant women. This is especially pertinent for women who have limited access to secondary/tertiary healthcare as those in remote settings, low-income countries or simply lack of out of hours laboratory services.

METHODS

The kit employs an absorptive column that separates Congo red dye bound to urinary misfolded protein from pregnant women and unbound dye. When a solution of Congo red dye pre-mixed with urine is loaded onto the absorptive matrix in a detection cuvette, the presence (positive) or absence (negative) of misfolded proteins can be determined based on the color of eluate collected in the lower section of the cuvette. 190 and 937 pregnant women who were >18 years old at the gestational age of ≥20 weeks were enrolled for the feasibility and validation cohort, respectively. The consistency between CercaTest Red and clinical diagnosis of PE according to the American College of Obstetricians and Gynecologist (ACOG) Guidelines was analyzed using the kappa statistic.

RESULTS

The POCT has a limit of detection (LoD) of human urinary misfolded proteins equivalent to 0.45 μM of denatured human serum albumin, with high reproducibility and stability. An accuracy of 96.84% for diagnosis of preeclampsia with a Kappa statistic of 0.746 (p < 0.001) was validated in a cohort of 937 subjects.

CONCLUSION

This test is easy to use, cost-effective and portable with short turnaround time and no laboratory instrument requirement. In the future, the test may have the potential to become quantitative using spectroscopy (Chinese Clinical Trial Registry No. ChiCTR1800017692).

Protein Misfolding in Pregnancy: Current Insights, Potential Mechanisms, and Implications for the Pathogenesis of Preeclampsia

Protein misfolding disorders are a group of diseases characterized by supra-physiologic accumulation and aggregation of pathogenic proteoforms resulting from improper protein folding and/or insufficiency in clearance mechanisms. Although these processes have been historically linked to neurodegenerative disorders, such as Alzheimer's disease, evidence linking protein misfolding to other pathologies continues to emerge. Indeed, the deposition of toxic protein aggregates in the form of oligomers or large amyloid fibrils has been linked to type 2 diabetes, various types of cancer, and, in more recent years, to preeclampsia, a life-threatening pregnancy-specific disorder. While extensive physiological mechanisms are in place to maintain proteostasis, processes, such as aging, genetic factors, or environmental stress in the form of hypoxia, nutrient deprivation or xenobiotic exposures can induce failure in these systems. As such, pregnancy, a natural physical state that already places the maternal body under significant physiological stress, creates an environment with a lower threshold for aberrant aggregation. In this review, we set out to discuss current evidence of protein misfolding in pregnancy and potential mechanisms supporting a key role for this process in preeclampsia pathogenesis. Improving our understanding of this emerging pathophysiological process in preeclampsia can lead to vital discoveries that can be harnessed to create better diagnoses and treatment modalities for the disorder.

Diagnostics of preeclampsia based on Congo red binding to urinary components: Rationales and limitations

Preeclampsia is a disorder that can occur during pregnancy and is one of the leading causes of death among pregnant women. This disorder occurs after the 20th week of pregnancy and is characterized by arterial hypertension, proteinuria, fetoplacental, and multiple organ dysfunctions. Despite the long history of studying preeclampsia, its etiology and pathogenesis remain poorly understood, and therapy is symptomatic. One of the factors of the disorder is believed to be misfolded proteins that are prone to form amyloid aggregates. The CRD tests, utilizing the binding of the amyloid-specific dye Congo red to urine components, demonstrate high efficiency in diagnosing preeclampsia. However, these tests have also been found to be positive in other disorders with proteinuria, presumably associated with concomitant amyloidosis. To assess the limitations of the CRD tests, we examined urine congophilia and protein components mediating Congo red positivity in patients with proteinuria, including preeclampsia, amyloid and non-amyloid nephropathies. We stained the urine samples and calculated congophilia levels. We also assessed the contribution of large protein aggregates to congophilia values using ultracentrifugation and determined the molecular weights of congophilic urinary proteins using centrifugal concentrators. All proteinuric groups demonstrate positive results in the CRD tests and congophilia levels were more than two times higher compared with the control non-proteinuric groups (p <0.01). There was a strong correlation between urine protein excretion and congophilia in amyloid nephropathy (rs = 0.76), non-amyloid nephropathies (rs = 0.90), and preeclampsia (rs = 0.90). Removal of large aggregates from urine did not affect the congophilia levels. Separation of urine protein fractions revealed congophilic components in the range of 30-100 kDa, including monomeric serum albumin. Our results indicate limitations of CRD tests in preeclampsia diagnostics in women with renal disorders and underscore the need for further research on the mechanisms of Congo red binding with urine components.

Urinary congophilia in pregnancy: a marker of kidney injury rather than preeclampsia

BACKGROUND

The differentiation between preeclampsia and similarly presenting kidney disease in pregnancy is a diagnostic challenge. Although some laboratory tests have been utilized, globally validated tools are yet needed, particularly in resource-limited settings. Congophilic proteins are abundantly detected in the urine of pregnant women who develop preeclampsia that is thought to be a marker of disease process. The present study aimed to assess the diagnostic and predictive utility of urinary congophilia in pregnant women with hypertensive disorders of pregnancy as well as kidney diseases.

METHODS

This cohort study included 157 pregnant women, classified as healthy controls ( n  = 38), preeclampsia/eclampsia ( n  = 45), gestational hypertension ( n  = 9), chronic hypertension ( n  = 8), chronic kidney disease (CKD) ( n  = 27), and pregnancy-related acute kidney injury (PR-AKI) ( n  = 30). Urinary congophilia was assessed by Congo Red Dot Blot assay.

RESULTS

Congo red retention (CRR) values were significantly higher in women with preeclampsia/eclampsia ( P  ≤ 0.001), chronic hypertension ( P  = 0.029), gestational hypertension ( P  = 0.017), CKD ( P  ≤ 0.001), PR-AKI secondary to preeclampsia ( P  ≤ 0.001), and PR-AKI secondary to other causes ( P  = 0.001), compared with healthy controls. Women with preeclampsia, CKD, and PR-AKI (non-preeclampsia related) exhibited the highest levels of CRR. CRR positively correlated to proteinuria ( P  = 0.006) and serum creatinine ( P  = 0.027). CRR did not significantly vary between women who presented antepartum and those presented postpartum after removal of the placenta ( P  = 0.707). CRR at a cut-off point of at least 1.272 had 91% specificity and 61.1% sensitivity in predicting renal recovery in PR-AKI patients. CRR had a poor specificity in discriminating preeclampsia from the other clinical presentations.

CONCLUSION

Urinary congophilia could not discriminate preeclampsia from similarly presenting kidney diseases in pregnancy. Further studies are needed to improve differentiation of these conditions.

A point-of care urine test to predict preeclampsia development in Asian women with suspected preeclampsia

OBJECTIVES

To evaluate the diagnostic performance and clinical utility of the urine Congo red dot test (CRDT) in predicting preeclampsia (PE) within 7 days, 14 days and 28 days of assessment.

STUDY DESIGN

A prospective single center double blind non-intervention study conducted from January 2020 to March 2022. Urine congophilia has been proposed as a point-of-care test for the prediction and rapid identification of PE. In our study, urine CRDT and pregnancy outcomes were assessed in women presenting with clinical features of suspected PE after 20 weeks of gestation.

RESULTS

Among the 216 women analyzed, 78 (36.1 %) women developed PE, in which only 7 (9.0 %) of them had a positive urine CRDT test. The median (IQR) interval between the initial test and the diagnosis of PE was significantly shorter for women with a positive urine CRDT compared with women with a negative urine CRDT (1 day (0-5 days) vs 8 days (1-19 days), P = 0.027). The negative predictive value of a negative urine CRDT test for PE within 7 days, 14 days and 28 days of assessment were 83.73 % (95 %CI 81.75 %- 85.54 %), 78.92 % (95 % confidence interval [CI] 77.07 %- 80.71 %) and 71.77 % (95 %CI 70.06 %- 73.42 %) respectively. The sensitivity of the urine CRDT in ruling in PE within 7 days, 14 days and 28 days of assessment were 17.07 % (95 %CI 7.15 %- 32.06 %), 13.73 % (95 %CI 5.70 %- 26.26 %) and 10.61 % (95 %CI 4.37 %- 20.64 %), respectively.

CONCLUSIONS

Urine CRDT alone has high specificity yet low sensitivity in the short-term prediction of PE in women with suspected PE. Further studies are required to evaluate its clinical utility.

The effectiveness of the Congo Red Dot paper test in hypertensive disorders of pregnancy: A systematic review and meta-analysis

Background

Congo Red Dot Paper Test (CRDPT) appears to be a simple, cost-effective, non-invasive diagnostic tool for hypertensive disorders of pregnancy (HDP). The main objective of the study is to assess the effectiveness of CRDPT in detecting HDP.

Methods

This is a systemic review and meta-analysis of published studies on the effectiveness of CRDPT in the detection of HDP. The study was conducted in line with the PRISMA-DTA guidelines. The PICOS framework was used to search for relevant articles using Medline, PubMed, Google Scholar, Web of Science, and the Cochrane Library databases. The articles were screened against a set of inclusion and exclusion criteria and analysed using the Review Manager 5.4 software.

Results

A title, abstract and full article screening was conducted on 18,153 potential articles based on the inclusion and exclusion criteria. The screening yielded five articles for meta-analysis. The total number of normotensive pregnant women (n = 3,380) in the included studies was five times higher than the total number of women with pre-eclampsia (n = 535). A difference between the HDP and normotensive group was noted. This is indicated by a significantly decreased in the effectiveness of CRDPT in detecting HDP as compared to normotensive group [Risk Ratio (RR) = 6.32 (2.17, 18.43) p < 0.00001]. The included studies had a high nature of heterogeneity (I ² = 98%, p < 0.00001) partially due to different study designs included in the analysis and different regions where studies were conducted given that none of these studies were conducted in African countries where HDP is prominent.

Conclusions

According to results generated from 5 studies in this meta-analysis, it was found that CRDPT might not be effective in the detection of hypertensive disorder of pregnancy. Moreover, more research, especially in African women where hypertensive disorders of pregnancy are prevalent, are re-quired to ascertain these findings.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021283679, identifier: CRD42021283679.

Proteomic Analysis of Maternal Urine for the Early Detection of Preeclampsia and Fetal Growth Restriction

Background: To explore the use of maternal urine proteome for the identification of preeclampsia biomarkers. Methods: Maternal urine samples from women with and without preeclampsia were used for protein discovery followed by a validation study. The targeted proteins of interest were then measured in urine samples collected at 20–24 and 30–34 weeks among nine women who developed preeclampsia, one woman with fetal growth restriction, and 20 women with uncomplicated pregnancies from a longitudinal study. Protein identification and quantification was obtained using liquid chromatography–tandem mass spectrometry (LC–MS/MS). Results: Among the 1108 urine proteins quantified in the discovery study, 21 were upregulated in preeclampsia and selected for validation. Nineteen (90%) proteins were confirmed as upregulated in preeclampsia cases. Among them, two proteins, ceruloplasmin and serpin A7, were upregulated at 20–24 weeks and 30–34 weeks of gestation (p < 0.05) in cases of preeclampsia, and could have served to identify 60% of women who subsequently developed preeclampsia and/or fetal growth restriction at 20–24 weeks of gestation, and 78% at 30–34 weeks, for a false-positive rate of 10%. Conclusions: Proteomic profiling of maternal urine can differentiate women with and without preeclampsia. Several proteins including ceruloplasmin and serpin A7 are upregulated in maternal urine before the diagnosis of preeclampsia and potentially fetal growth restriction.