An elevated level of urinary nephrin (nephrinuria) may be associated with an increased risk of preeclampsia (PE), according to a study, suggesting that a certain cut-off can facilitate identification of women with greater PE risk.
Researchers investigated the feasibility of nephrinuria use to assess the risk of PE by enrolling 89 pregnant women without hypertension or significant proteinuria in pregnancy (SPIP). The number of urine samples obtained was 31 during the first trimester, 125 during the second, and 93 during the third. Outcomes were changes in nephrin:creatinine ratio (NCR) and protein:creatinine ratio (PCR). SPIP was defined as PCR >0.27.
PE occurred in 14 of the women. In this group of women, NCR positively correlated with PCR (correlation coefficient, 0.862; p<0.0001).
However, there were no significant changes in NCR even with marked increases in PCR among 75 women with normotensive pregnancies. This shows that the increase in nephrinuria over the physiological range of proteinuria in pregnancy was small.
The risk of later PE development was greater among asymptomatic women with NCR >122 ng/mg (95th centile value for 75 women with normotensive pregnancies) than among those with NCR ≤122 during both the second trimester (relative risk [RR], 5.93; 95 percent CI, 2.59 to 13.6; 60 vs 10 percent) and third trimester (RR, 13.5; 3.31 to 55; 75 vs 5.5 percent).
Nephrin is a protein that is predominantly found at the glomerular slit diaphragm of podocytes. Previous studies have reported that nephrin expression is reduced in kidney biopsy specimens from women with PE and in autopsy specimens from women who died from PE. The reduced expression may be linked to increased shedding of nephrin from podocytes.
The findings suggest that NCR is unlikely to increase in normal pregnancy despite the gradual increases in PCR, whereas both NCR and PCR increase gradually with advancing gestation in PE pregnancies, researchers said. This indicates that urinary NCR may prove more useful in identifying women who are at higher risk of PE compared with urinary PCR.