821: Brain-type natriuretic peptide (BNP) as a diagnostic tool in preeclampsia

Brain-type natriuretic peptide (BNP) is synthesized in cardiac ventricles in response to volume expansion and is approved to diagnose congestive heart failure in patients with dyspnea. This double-blind study examined the relationship between BNP and severity of preeclampsia and further evaluated its use as a diagnostic tool. Participants were recruited on Labor and Delivery at Wesley Medical Center. Sixty-six BNP levels were obtained from women who were being evaluated for preeclampsia. An additional 30 patients were recruited as controls. Plasma BNP values were determined using a standard assay. Final diagnosis was determined after the patient delivered. BNP levels increased with severity of disease. The control group′s mean and median BNP were 44.3 and 32.0 pg/ml respectively. BNP values increased in patients diagnosed with gestational hypertension and further with mild preeclampsia. The highest values were in severe preeclamptics with a mean of 216.6 and a median of 134.0 pg/ml. This trend was significant (p<0.001), and also when mild preeclamptics were compared with severe preeclamptics (p=0.008). A BNP cut-off of 82.5 pg/ml had a negative predictive value (NPV) of 94% for excluding severe preeclampsia in this study. The NPV increased to 99% using the severe preeclampsia prevalence at Wesley Medical Center of 3.5%. This cut-off had a sensitivity of 79%, a specificity of 80%, and an accuracy of 80%. When coupled with blood pressure elevation, tobacco use lowered BNP levels compared to those of non-smokers. (p = 0.043) BNP values increase with severity of disease and a threshold of 82.5 pg/ml can be used to exclude the diagnosis of severe preeclampsia. Until further investigation, this threshold should not be used to rule out severe preeclampsia in patients who use tobacco.