November 22, 2011 (Philadelphia, Pennsylvania) — Podocyturia, the appearance of kidney podocyte cells in the urine, appears to be an early and specific predictor of preeclampsia (PE).
Currently, there are no tests that predict the development of PE, Iasmina Craici, MD, from the division of nephrology at St. Louis University in Missouri, told a news conference here at Kidney Week 2011: American Society of Nephrology 44th Annual Meeting. She is lead author of a study on podocyturia during pregnancy, which was conducted when she was at the Mayo Clinic in Rochester, Minnesota.
She explained that although both PE and gestational hypertension involve elevated blood pressure, PE is distinguished by protein in the urine. In gestational hypertension, there is no proteinuria; however, gestational hypertension can progress to PE.
PE affects 3% to 5% of all pregnancies, making it the most common medical complication of pregnancy. Although most cases are mild, severe disease occurs in 25% of cases, and can lead to maternal or fetal death.
Podocyturia results when epithelial podocyte cells from within the glomerulus detach and are shed in the urine. In this study, urine was collected from pregnant women, and cells in the urine were cultured overnight and then prepared and stained for podocin, a protein specific to podocytes.
The researchers followed 267 women with singleton pregnancies and successful deliveries from their first prenatal visit to delivery. Urine specimens for podocyte analysis were collected at midterm (gestational weeks 25 to 28) and just before delivery.
Fifteen of the women developed PE and 15 developed gestational hypertension. Control subjects (n = 45) were selected from the normal pregnancies.
Dr. Craici reported that at midterm, none of the women with normal pregnancies or with gestational hypertension had podocyturia. "However, all 15 preeclamptic patients had podocyturia at midgestation; this is the time when actually none of the clinical symptoms have developed. They did not have hypertension, [and] they did not yet have proteins in the urine," she said.
All 15 of these women would go on to develop PE and hemolysis, elevated liver enzymes, and low platelet count (HELLP syndrome).
At delivery, the investigators found that podocyturia was present in women with PE/HELLP syndrome but absent in those with gestational hypertension and in normotensive control subjects.
Podocyturia During Pregnancy
| Group | At Midpregnancy, n (%) | At Delivery, n (%) |
| Normotensive | 0 of 45 (0) | 0 of 45 (0) |
| Gestational hypertension | 0 of 15 (0) | 1 of 15 (7) |
| Preeclampsia | 15 of 15 (100) | 15 of 15 (100) |
Dr. Craici predicted that the podocyte test will become a useful tool for healthcare providers treating pregnant women. "Currently, there are no tests that can reliably predict who will develop preeclampsia later in pregnancy. This test can help physicians identify women at risk of developing preeclampsia later in their pregnancy, and it will give us the opportunity to implement early treatment of severe high blood pressure, which may improve maternal and fetal outcomes," she said. However, improvements in the test are still needed, such as faster and observer-independent testing methods.
Delphine Tuot, MD, MAS, assistant professor of nephrology at the University of California at San Francisco, who moderated the news conference and was not involved in the study, told Medscape Medical News that she hopes this research-phase test reaches clinical practice.
"I think the ability to even screen somebody at higher risk for preeclampsia will mean that that individual will get more testing throughout the second half of their pregnancy, or at least more monitoring, and that may be very helpful in trying to improve maternal and fetal outcomes," she said.
At this point, she noted, the test needs to be validated in a wider population of pregnant women. Although the test appears to have both good positive and negative predictive value, "I think we have to be careful to [not] actually label its sensitivity and specificity. It's a very small cohort that's not diverse or nationally representative, so I would hesitate to use those words. But it's very exciting," Dr. Tuot said.
Dr. Craici and Dr. Tuot have disclosed no relevant financial relationships. Coauthor Vesna Garovic, MD, is the inventor of the technology used in the research, which has been licensed to a commercial entity; Dr. Garovic and the Mayo Clinic have contractual rights to receive royalties through that license.
Kidney Week 2011: American Society of Nephrology 44th Annual Meeting. Abstract FR-OR292. Presented November 11, 2011.
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