THE CLINICAL UTILITY OF SERUM URIC-ACID MEASUREMENTS IN HYPERTENSIVE DISEASES OF PREGNANCY

OBJECTIVE: Our purpose was to evaluate the clinical utility of serum u ric acid measurements in the hypertensive diseases of pregnancy. STUDY DESIGN: We performed a nested case-control study to assess the clinic al utility of serum uric acid measurements in women with hypertensive diseases of pregnancy. We identified 344 women who had serum uric acid measurements at term and categorized them into five diagnostic groups according to definitions of hypertensive diseases in pregnancy publis hed by the National Working Group on Hypertension in Pregnancy: transi ent hypertension of pregnancy (n = 69), preeclampsia (n = 130), chroni c hypertension (n = 23), chronic hypertension with superimposed preecl ampsia (n = 29), and normal (n = 93). We compared the mean uric acid c oncentration for each group with use of a one-way analysis of variance and Scheffe's post hoc test and calculated the sensitivities and spec ificities in diagnosing preeclampsia as well as the likelihood ratios for serum uric acid values of 5.5, 6.0, and 6.5 mg/dl. We also examine d the correlation between serum uric acid levels and several clinical outcome measures in women with hypertensive diseases of pregnancy RESU LTS: The mean serum uric acid values for women with preeclampsia (6.2 +/- 1.4 mg/dl) and transient hypertension (5.6 +/- 1.7 mg/dl) were sig nificantly higher than those of controls (4.3 +/- 0.8 mg/dl, p < 0.05) . The difference in mean serum uric acid values between women with chr onic hypertension (4.9 +/- 1.0 mg/dl) and superimposed preeclampsia (5 .8 +/- 1.4 mg/dl) were not statistically significant. The likelihood r atio of having preeclampsia with a serum uric acid value of 5.5 mg/dl was 1.41 in gestational hypertension of pregnancy and 2.5 in chronic h ypertension. With use of a receiver-operator characteristic curve, we were unable to identify a serum uric acid value that could be used to differentiate various hypertensive diseases of pregnancy. There was a weak correlation between serum uric acid values and several clinical o utcome measures of preeclampsia (r = 0.06 to 0.26). CONCLUSION: Althou gh mean serum uric acid values are elevated in women with preeclampsia , the clinical utility of serum uric acid values in differentiating va rious hypertensive diseases of pregnancy appears to be limited. In the setting of chronic hypertension, however, a serum uric acid level of greater than or equal to 5.5 mg/dl could identify women with an increa sed likelihood of having superimposed preeclampsia.