Urine Congo red test for the detection of preeclampsia in pregnant women presenting with suspected preeclampsia

Abstract

Objectives

To determine the predictive performance of the urine Congo red point-of-care test for the identification of preeclampsia in women presenting with suspected preeclampsia.

Methods

A prospective multi-center cohort study was conducted to include women with suspected preeclampsia (n = 244). The urine Congo red test was determined (score range 1–8). The diagnosis of preeclampsia was based on criteria proposed by The American College of Obstetricians and Gynecologists. The primary outcome was the predictive performance (sensitivity, specificity, negative and positive predictive values, as well as likelihood ratios) of the Congo red kit test for the diagnosis of preeclampsia.

Results

Fifty-four percent (131/244) of women with suspected preeclampsia subsequently developed preeclampsia. The sensitivity and specificity of the urine Congo red test were 49.6% and 94.7%, respectively, when using a cutoff for Congo red ≥4. The test had a significant positive correlation with the level of urine protein (Pearson correlation 0.61, p-value <.01). Intra- and inter-observer reliabilities were good (intra-class correlation coefficient and Cohen’s kappa coefficient of 0.88 and 0.75, respectively; p < .01).

Conclusion

The urine Congo red kit test has a high positive predictive performance for the identification of preeclampsia with high reproducibility. This test may be used as a bed side test to rule-in the diagnosis of preeclampsia in women presenting with suspected preeclampsia.

Keywords:

• Congo red kit test
• misfolded proteins
• point-of-care test
• preeclampsia
• urine congophilia

Acknowledgments

We thank all participants, our staff and faculty for their support.

Authors contributions

Conceptualization, sample collection, patient management, original draft preparation and finalization: P.T. and P.C. Substantial contributions to sample collection, patient management and finalization of the manuscript: K.R., N.Y. and N.C. All authors read and approved the final manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are available from the corresponding author, P.T., upon reasonable request.

Additional information

Funding

This research was supported by the Faculty of Medicine Ramathibodi Hospital, Mahidol University (RF 65118 and A26/2564) and the Office of the Permanent Secretary, Ministry of Higher Education, Science, Research and Innovation [Grant No. RGNS 64-157].