There are a number of cardiac biomarkers used in classifying different aspects of cardiac pathology. The BNP and NT-proBNP are measures of myocyte stretch – the prohormone pro-BNP is cleaved into BNP and NT-proBNP. Assays in different clinical settings may measure one or more of these markers. The most potent inducer of BNP transcription is left ventricular wall stretch due to increased pressure or volume. BNP is cleared by a number of organs, including the kidneys. The sensitivity of this test has been demonstrated in a number of studies (such as the Breathing Not Properly Multinational Study) at various cutoff points, approaching 90% or greater. The specificity of the test is less robust (ranging from 60-90% depending on cutoff points). Aside from heart failure, a number of other cardiopulmonary disorders may be associated with an elevated BNP, including acute coronary syndrome, myocarditis, valvular heart disease, hypertrophic cardiomyopathy, atrial fibrillation/flutter, right ventricular dysfunction in the setting of pulmonary disease. Some other comorbidities, including renal dysfunction and critical illness may be associated with higher BNP levels. That being said, the highest values and cutoffs are consistently observed in patients who have systolic dysfunction (particularly symptomatic systolic left ventricular dysfunction).
References: Cardiac Biomarkers and Heart Failure