Accuracy of serum uric acid in predicting complications of pre-eclampsia: a systematic review.

BACKGROUND

Pre-eclampsia is one of the largest causes of maternal and fetal mortality and morbidity. Hyperuricemia is often associated with pre-eclampsia.

OBJECTIVE

To determine the accuracy with which serum uric acid predicts maternal and fetal complications in women with pre-eclampsia.

STUDY DESIGN

Systematic quantitative review of test accuracy studies.

SEARCH STRATEGY

We conducted electronic searches in MEDLINE (1951-2004), EMBASE (1980-2004), the Cochrane Library (2004:4) and the MEDION database to identify relevant articles. A hand-search of selected specialist journals and reference lists of articles obtained was then carried out. There were no language restrictions for any of these searches.

SELECTION CRITERIA

Two reviewers independently selected the articles in which the accuracy of serum uric acid was evaluated to predict maternal and fetal complications of pre-eclampsia.

DATA COLLECTION AND ANALYSIS

Data were extracted on study characteristics, quality and accuracy to construct 2 x 2 tables with maternal and fetal complications as reference standard. Summary likelihood ratios for positive (LR+) and negative LR(-) test results are generated for various threshold levels of uric acid.

MAIN RESULTS

There were 18 primary articles that met the selection criteria, including a total of 3913 women and forty-one 2 x 2 tables. In women with pre-eclampsia, a positive test result of uric acid greater than or equal to a 350-micromol/l threshold predicted eclampsia with a pooled likelihood ratio (LR) of 2.1 (95% CI 1.4-3.5), while a negative test result had a pooled LR of 0.38 (95% CI 0.18-0.81). For severe hypertension as the outcome measure, the LRs were 1.7 (95% CI 1.3-2.2) and 0.49 (95% CI 0.38-0.64) for positive and negative test results, respectively, and for caesarean section the LRs were 2.4 (95% CI 1.3-4.7) and 0.39 (95% CI 0.20-0.76). For stillbirths and neonatal deaths the respective LRs were 1.5 (95% CI 0.91-2.6) and 0.51 (95% CI 0.20-1.3). For the prediction of small-for-gestational-age fetus, the pooled LRs were 1.3 (95% CI 1.1-1.7) and 0.60 (95% CI 0.43-0.83) for positive and negative results, respectively. AUTHOR'S CONCLUSION: Serum uric acid is a poor predictor of maternal and fetal complications in women with pre-eclampsia.