Evaluation of Congo red staining kit to determine proteinuria in preeclampsia

Abstract

Introduction: Preeclampsia is characterised by the increased excretion of misfolding protein, attracted by a Diazo dye denominated congo red. Aim: To compare congo red staining kit versus a urocolor test to determine proteinuria in patients with preeclampsia. Materials and Methods: This was a prospective, transversal study, performed between August 2010 to July 2011, including pregnant and puerperal women with the clinical diagnosis of preeclampsia. From all patients, a single sample of 24 hours urine was tested with congo red to determine the presence of proteinuria, comparing the qualitative results of the urine dipstick for proteinuria and the gold standard determination of protein in 24 hours urine collection. Differences among nominal conditions were evaluated by the Mann-Whitney U-test. Results: A total of 50 pregnant and puerperal women were included in this study. The statistical comparison between 2 vs. 3, 2 vs. 4 and 3 vs. 4, congo red positive fields reached significant difference (p≤0.001) in relation to the mean proteinuria values for each one. In contrast, with the urocolor test there were no differences per number of positive crosses. Conclusion: The congo red has a high selectivity for beta-folded proteins in preeclampsia being a promising screening test of high value to the clinician.