Screening for late preeclampsia at 35–37 weeks by the urinary Congo-red dot paper test

Abstract

Background: Several cross-sectional studies have investigated the incidence of urinary Congored dye positivity in women with preeclampsia (PE), compared to unaffected pregnancies, and reported very high sensitivity and low false positive rate in the diagnosis of PE. Objective: To determine the performance of the urinary Congo-red dot paper test at 35-37 weeks' gestation in the prediction of delivery with PE at 2 and >2 weeks after assessment. Methods: This was a prospective observational study in women attending for a routine hospital visit at 35 þ0 to 36 þ6 weeks' gestation in a maternity hospital in England. Urine samples were collected and the Congo-red dot paper test was used to assess the degree of Congo-red dye positivity. The test uses a scoring system from 1 to 8 and the higher the score the greater the degree of Congo-red dye positivity. We examined and compared the degree of Congo-red dye positivity in the groups that delivered with PE at 2 and >2 weeks with those that remained normotensive. Reproducibility was assessed by examining the inter-and intra-observer reliability of scoring on stored images with the researchers blinded to previous results. Results: The study population of 2140 women included 46 (2.1%) that subsequently developed PE (2.1%). The urinary Congo-red dot test was positive in 8.3% (1/12) and 2.9% (1/34) that delivered with PE at 2 and >2 weeks from assessment and in 0.2% (4/2094) of the unaffected pregnancies when the cutoff for Congo-red dye positivity was !5. The respective values when the cutoff used was !3 were 66.7%, 23.5%, and 16.5%, respectively. The intraclass correlation coefficient for the inter-observer reliability was 0.926 (95% CI 0.890-0.953, p<.0001) and Cohen's kappa coefficient for the intra-observer reliability was 0.904, p<.0001. Conclusions: The performance of the urinary Congo-red dot paper test at 35-37 weeks' gestation in the prediction of PE is very poor.

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

“…Our findings showed that CRDPT is not effective in the diagnosis of HDP (Figure 2). Our findings are in support of Dorbert et al, who reported that the performance of CRDPT in diagnosing PE is poor (27). Furthermore, a study by McCarthy et al that evaluated urinary congophilia levels in women with PE, chronic kidney disease without PE, and lupus nephritis in non-pregnant women, confirmed that the CRDPT cannot differentiate between these conditions, suggesting that CRDPT is not a reliable tool in the prediction of PE or HDP (26).…”

“…These findings designate the variance in pathology of the two classes of PE (26). In contradiction to results reported thus far, Dobert et al reported that the CRDPT results were "poor" in women between 35 and 37 weeks of gestation (27).…”

“…In a study by Bracken et al, 204 were pre-eclamptic and 205 normotensive women, the CRDPT was found to be effective in 155 and 50 respectively ( 30 ). In a study by Dobert et al which included 46 pre-eclamptic and 2,094 pregnant normotensives, the CRDPT was found to be effective in 2 and 4 respectively ( 27 ). Rood et al included 112 pre-eclamptics and 234 normotensives, the CRDPT was found to be effective in 96 and 138 respectively ( 22 ).…”

“…recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-analysis for Protocols (PRISMA-DTA) guidelines 2020 ( 27 ). The results were reported based on the PRISMA 2015 ( 28 ), statement and article screening and the selection process was demonstrated through a PRISMA- P flow diagram.…”

“…Summary of all the studies that used the Congo Red Dot test to Diagnose Hypertensive Disorders of Pregnancy. In a study by Dobert et al which included 46 pre-eclamptic and 2,094 pregnant normotensives, the CRDPT was found to be effective in 2 and 4 respectively(27). Rood et al included 112 pre-eclamptics and 234 normotensives, the CRDPT was found to be effective in 96 and 138 respectively(22).…”