Elevation of the serum uric acid level preceding the clinical manifestation of preeclampsia in twin pregnancies.

To assess changes in the serum uric acid level in the third trimester of twin pregnancies, a total of 152 consecutive women with twin pregnancies were examined. Serum uric acid levels were analyzed in the women at varying gestational weeks in the presence or absence of preeclampsia. A receiver operating characteristic curve was used to determine the optimal cutoff value of serum uric acid between 30 and 31 weeks of gestation predicting subsequent development of preeclampsia. Forty-four women (29%) developed preeclampsia (preeclampsia group) at 33.2 +/- 1.9 weeks (mean +/- SD) and gave birth at 35.4 +/- 1.5 weeks of gestation. The remaining 108 women (71%) gave birth at 35.6 +/- 1.7 weeks of gestation (control group without preeclampsia). Serum uric acid levels rose gradually with advancing gestation in both groups. In the preeclampsia group, they were already increased at 30-31 weeks of gestation and corresponded to those seen in the control group at 37 weeks. The cutoff value at 30-31 weeks was 5.5 mg/dl, with a sensitivity of 73% and a specificity of 74%. These results suggest that an elevation in serum urate preceded the onset of preeclampsia. Determination of the serum level of uric acid between 30 and 31 weeks of gestation was useful for detecting a higher risk of late-onset preeclampsia in twin pregnancies.