Utilization of Serum BNP to Distinguish Pre-Eclampsia From Hypertension in Pregnancy

Preeclampsia is a frequent complication of pregnancy. The chief concern is that preeclampsia may progress to end-organ damage, with resultant deterioration of both the mother and the fetus. As a result, women with significant preeclampsia may have their labor accelerated or even require caesarian section. The diagnosis is made based on a constellation of non-specific symptoms, including headache, vision changes, proteinuria, and hypertension. The diagnosis becomes even more difficult to establish when the patient has chronic hypertension prior to her pregnancy.

In many Emergency Departments across the country, emergency physicians are faced with patients that have had either sporadic or non-existent prenatal care. Patients may often not know what their blood pressure was before their pregnancy. Records may not exist or be available for the emergency physician to make an accurate decision. Patients are often transferred to a tertiary care center for obstetrical admission when the diagnosis is unclear, as outlying areas are increasingly without obstetrical coverage. The availability of a sensitive and specific test for the presence of preeclampsia, or gestational hypertension superimposed on chronic hypertension, would allow the emergency physician to avoid costly hospital admissions or transfers while provide safe and effective care for the patient.

B-type or brain type natriuretic peptide (BNP) is a 32-amino acid peptide secreted primarily by the cardiac ventricles under conditions of ventricular wall strain. In addition, it has been demonstrated that BNP is also secreted in the human amnion during pregnancy. Small studies in the international literature suggest that serum BNP is elevated in preeclamptic patients and patients with chronic hypertension in pregnancy. A novel fluorescent immunoassay technique, the Biosite Triage BNP assay, utilizes murine fluorescent labeled antibodies to detect and quantify serum BNP levels. The Triage assay is designed for clinical use, with an estimated laboratory turnaround time of fifteen minutes (Biosite Triage BNP product insert). The Triage assay has gained acceptance as a highly sensitive and specific tool to assist in the rapid diagnosis of congestive heart failure exacerbation; its utility in the preeclamptic population has not been assessed.