The Emerging Roles of BNP and Accelerated Cardiac Protocols in Emergency Laboratory Medicine

Charis Hainaut; Wayne Gade

doi:10.29074/ascls.16.3.166

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Charis Hainaut, CLS(NCA)
1. is a CLS in the Clinical Laboratory, Decatur Memorial Hospital, Decatur IL
Wayne Gade, PhD MT(ASCP)⇑
1. is assistant Professor of Clinical Laboratory Science, University of Illinois at Springfield, Springfield IL

Address for correspondence: Wayne Gade PhD MT(ASCP) Clinical Laboratory Science Program, HSB 314, University of Illinois at Springfield, Springfield, IL 62703-5407. (217) 206-7349.

After reading the following articles, the reader will demonstrate his/her understanding of the material by achieving the following:

Describe the biochemistry of the BNP and the other natriuretic peptides.
Describe the major physiologic responses to the elevation of BNP levels.
Discuss the mechanism by which the binding of BNP to the target cell results in alteration of Na⁺ and water reabsorption.
Describe the formation of arterial plaque and the development of coronary artery disease and acute coronary syndromes (ACS).
Describe the physiological conditions that develop into CHF and cause the release of BNP.
Describe and interpret the diagnostic accuracy, sensitivity, specificity, and negative predictive values reported for rapid BNP assays.
Describe the trend toward “accelerated cardiac protocols,” including which markers are suggested, and the suggested time-course of sequential testing.
Evaluate patient data and derive appropriate diagnostic conclusions.
Discuss the use of BNP for prognosis and screening of patients for LV dysfunction.
Discuss the interpretations of slightly elevated levels of troponin and C - reactive protein (CRP) as they relate to ACS and risk analysis.

Abstract

BACKGROUND: The role of the clinical laboratory in emergency cardiac medicine is rapidly evolving; with recent redefinitions of acute myocardial infarction (AMI) and unstable angina (UA) based on troponin levels, recommended acceleration of cardiac testing protocols, and increased clinical measurement of B-type natriuretic peptide (BNP). We briefly review the background pathophysiology of acute coronary syndromes (ACS) and congestive heart failure (CHF), along with an overview of the biochemistry and physiology of the natriuretic peptides.

METHODS: The assay principles and performance characteristics of the rapid BNP assays are discussed. The performance characteristics of troponin assays are at the center of controversy regarding the redefinition of AMI and UA, and will be discussed.

RESULTS: We review the rapidly expanding evidence regarding the clinical utility of BNP for CHF patients. While BNP has gained wide acceptance as a rapid diagnostic tool, considerable controversy remains concerning its potential for prognosis, screening, and therapeutic monitoring. Although a thorough discussion of the use of cardiac markers is well beyond the scope of this review, overviews of the redefinitions of AMI and UA, and the trend toward accelerated testing protocols to obtain a quicker diagnosis or ruling-out of AMI are included. In addition to accelerating the retesting of existing markers, a recent test for ischemia modified albumin (IMA) promises another quantum leap in cardiac diagnoses.

CONCLUSIONS: The positive impact of these developments on the healthcare costs and overall improvement in the quality of healthcare delivery will be discussed. A brief analysis of the downstream costs of BNP testing is also offered.

ABBREVIATIONS: ACS = acute coronary syndromes; AMI = acute myocardial infarction; BNP = B-type natriuretic peptide; CHF = congestive heart failure; COPD = chronic obstructive pulmonary disease; ECG = electrocardiogram; ED = emergency department; hsCRP = high sensitivity C-reactive protein; IMA = ischemia modified albumin; LV = left ventricular; MI = myocardial infarction; NCAB = National Academy of Clinical Biochemists; NPV = negative predictive value; NYHA = New York Heart Association; PE = pulmonary embolism; RAAS = renin-angiotensin-aldosterone system; RV = right ventricular; UIA = unstable I angina.