Can antenatal clinical and biochemical markers predict the development of severe preeclampsia?

OBJECTIVE: This study was undertaken to develop a multivariable clinical pr edictive rule for severe preeclampsia using second-trimester clinical facto rs and biochemical markers. STUDY DESIGN: We performed a retrospective cohort study of all pregnant pat ients with single gestations from 1995 through 1997 for whom we had complet e follow-up data, Through medical record review we determined whether patie nts had severe preeclampsia develop according to American College of Obstet ricians and Gynecologists criteria. Case patients with severe preeclampsia were compared with control subjects with respect to clinical data and multi ple-marker screening test results. With potential predictive factors identi fied in the bivariate and stratified analyses both an explanatory logistic regression model and a clinical prediction rule were created. Patients were assigned a predictive score according to the presence or absence of predic tive factors, and receiver operating characteristic analysis was used to de termine the optimal score cutoff point for prediction of severe preeclampsi a with maximal sensitivity. RESULTS: Among the 1998 patients we found 49 patients with severe preeclamp sia (prevalence, 2.5%). After we controlled for confounding variables, case patients and control subjects had similar human chorionic gonadotropin and alpha-fetoprotein levels, and the only variables that remained significant ly associated with severe preeclampsia were nulliparity (relative risk, 3.8 ; 95% confidence interval. 1.7-8.3), history of preeclampsia (relative risk , 5.0; 95% confidence interval, 1.7-17.2), elevated screening mean arterial pressure (relative risk, 3.5; 95% confidence interval, 1.7-7.2), and low u nconjugated estriol concentration (relative risk, 1.7; 95% confidence inter val, 0.9-3.4). Our predictive model for severe preeclampsia, which included only these 4 variables, had a sensitivity of 76% and a specificity of 46%. CONCLUSION: Even after incorporation of the strongest risk factors, our pre dictive model had only modest sensitivity and specificity for discriminatio n of patients at risk for development of severe preeclampsia. The addition of the human chorionic gonadotropin and a-fetoprotein biochemical markers d id not enhance the model's predictive value for severe preeclampsia.