PHILADELPHIA – The detection of urinary podocytes in mid-pregnancy is a highly sensitive and specific marker for preeclampsia and may be the first reliable tool for predicting which women will develop the potentially life-threatening hypertensive complication, according to Dr. Iasmina M. Craici.
Previously, investigators determined that the urinary excretion of viable podocytes (glomerular epithelial cells) was significantly higher in patients with preeclampsia, compared with normotensive patients, and that it had a greater positive predictive value for diagnosing preeclampsia than certain specific angiogenic factors of the condition (Am. J. Obstet. Gynecol. 2007;196:320.e1-7).
"There are currently no tests that will reliably predict who will develop preeclampsia, so the possibility of being able to identify, in mid-gestation, those women who will later go on to develop preeclampsia is especially important," Dr. Craici stated. "It will give us the opportunity to implement early treatment of severe high blood pressure and by doing so will improve maternal and fetal outcomes," she said.
The current study was designed to ascertain whether podocyturia is present in the urine before the onset of preeclampsia and whether it can be used to differentiate between preeclampsia, gestational hypertension, and normal pregnancy, said Dr. Craici of the Mayo Clinic in Rochester, Minn.
From a prospective cohort of 315 patients, 267 successful deliveries were included in the final analysis. Of these, 204 women had normal pregnancies and 30 had hypertensive pregnancies, including 15 cases each of preeclampsia and gestational hypertension, Dr. Craici reported at Kidney Week 2011, sponsored by the American Society of Nephrology. The remaining 33 pregnancies were complicated by other problems, including gestational diabetes, intrauterine growth retardation, and preterm delivery, she said.
All patients had their blood pressure and protein/creatinine ratios checked at mid-gestation (weeks 25-28), prior to the onset of preeclampsia or gestational hypertension. Urine sediments collected in mid-pregnancy, prior to 210 days gestation, were cultured for 24 hours to select for viable cells, "and we identified podocytes using podocin staining," Dr. Craici explained. For purposes of the comparative analysis, 45 patients were selected from the normal pregnancy group as controls, she said, noting that there was no age difference between the groups.
At mid-pregnancy, "none of the 45 normotensive or the 15 gestational hypertensive women had podocyturia present in their urine specimens, but it was present in the urine of all of the preeclamptic women," said Dr. Craici. At this time point, she said, none of the women who would later develop preeclampsia had signs of the condition. "They did not have hypertension, nor did they yet have protein in the urine."
At delivery, podocyturia was again absent in all of the normotensive pregnancies and present in all of the preeclamptic pregnancies, Dr. Craici said, noting that it was present in only one of the women with gestational hypertension.
Dr. Craici disclosed that the technology used in this research has been licensed to a commercial entity and that senior investigator Dr. Vesna D. Garovic and the Mayo Clinic have contractual rights to receive royalties from the licensing of the technology.