We analysed samples from women with pre-eclampsia (n=23), gestational hypertension (10), chronic kidney disease (28), chronic hypertension (14), chronic kidney disease with superimposed pre-eclampsia (5), chronic hypertension with superimposed pre-eclampsia (12), and healthy pregnant controls (31). Samples from healthy non-pregnant controls (n=10) and non-pregnant women with systemic lupus erythematosus either with (25) or without lupus nephritis (14) were analysed. Urinary congophilia was quantified by measurement of congo red retention (CRR) and compared between groups.
A significant increase in congophilia was detected in urine from women with pre-eclampsia (median CRR 47%, IQR 22–68) compared with healthy pregnant controls (16, 13–21; p=0·002), women with gestational hypertension (20, 13–27; p=0·008), or women with chronic hypertension (17, 12–28; p=0·01). Congophilia was also present in pregnant women with chronic kidney disease and was not significantly different from those with pre-eclampsia or women with chronic kidney disease and superimposed pre-eclampsia. Non-pregnant women with lupus nephritis had significantly higher congophilia retention than did non-pregnant controls (38%, 17–73 vs 9, 7–11; p<0·0001) and non-pregnant women with systemic lupus erythematosus but no lupus nephritis (13, 11–17; p=0·001).
This study confirms the presence of urinary congophilia, as assessed by CRR, in women with pre-eclampsia but demonstrates that it is similarly present in other conditions associated with renal impairment in pregnant and non-pregnant women.
This work was supported by funding from Tommy's Charity UK, an Academy of Medical Sciences UK Starter Grant for Clinical Lecturers, and the National Institute for Health Research (NIHR) Biomedical Research Centre at Guy's and St Thomas' NHS Foundation Trust and King's College London. FPM is funded by a NIHR Clinical Academic Fellowship.