BACKGROUND AND PURPOSE:

• Previous research from this group showed that in preeclampsia, an underlying mechanism may be a protein conformational disorder (abnormal changes in protein size or shape)
• Proteins in the urine of preeclamptic women bind to Congo Red dye, resulting in a phenomenon known as urine congophilia
• Rood et al. (Lancet E Clinical Medicine, 2019) assessed the utility of a paper-based point-of-care test to detect congophilia for rapid preeclampsia triage and diagnosis

METHODS:

• Prospective cohort study
• Participants
  • Pregnant women evaluated for PE in L&D triage
• Study design
  • Congo Red Dot (CRD) Paper Test (index test) was performed on fresh urine samples
  • CRD Paper Test results were compared to an expert adjudicated diagnosis in each case (2 MFMs blinded to results)
  • Accuracy of the CRD Paper Test was also compared to other urine and serum analytes relevant to preeclampsia diagnosis  
    • Placental growth factor (PlGF)
    • Soluble fms-like tyrosine kinase-1 (sFlt-1)

RESULTS:

• 346 women
  • Clinical diagnosis of PE in triage: 32%
  • Admitted for PE workup: 63%
• CRD Paper Test
  • Positive: 25%
  • Adjudication confirmed: 28%
• CRD Paper Test performance
  • 80.2% sensitivity
  • 89.2% specificity
  • 92.1% negative predictive value
  • 86.7% accuracy
• While pre-test probability was 27.7%, following testing
  • PPV: 74.0%
  • NPV: 92.1%
• CRD Paper Test outperformed measured serum and urine markers, based on the following AUC ROC data
  • CRD Paper Test: 0.850 (95% CI, 0.808 to 0.886)
  • sFlt-1: Urine 0.723 [95% CI, 0.673 to 0.770) | Serum 0.809 (95% CI, 0.753 to 0.856)
  • PlGF:  Urine 0.678 (95%. CI, 0.625 to 0.727) | Serum 0.474 (95% CI, 0.687 to 0.801)
  • Urine sFlt-1/PlGF: 0.765 (95% CI, 0.716 to 0.809)

CONCLUSION:

• The CRD Paper Test outperformed previous diagnostic markers for preeclampsia
• The authors state that

CRD Paper Test is an accurate, low technology, easy to use triage diagnostic tool that allows for accurate identification of PE within minutes

Learn More – Primary Sources:

Congo Red Dot Paper Test for Antenatal Triage and Rapid Identification of Preeclampsia

Related ObG Topics:

Which Markers Can We Use to Screen for Early and Late Preeclampsia?

Does Placental Growth Factor Lead to a Quicker Diagnosis in Women with Suspected Pre-Eclampsia?

How Well Can Uric Acid Levels Predict Preeclampsia Complications?