Diagnostic Use
BNP is a 32 amino acid hormone secreted from cardiac myocytes subjected to increased ventricular wall stress.
NT-proBNP is the inactive cleavage product of the secretion of BNP and is used as a marker of BNP. Its half-life is approximately 40 minutes, compared with a half-life of approximately 20 minutes for active BNP. Our lab measures NT-proBNP.
Causes of elevated BNP or NT-proBNP
Cardiac:
Congestive Heart Failure
Acute Coronary Syndromes
Left Ventricular Hypertrophy
Hypertrophic & Restrictive Cardiomyopathy
Constrictive Pericarditis
Valvular Heart Disease
Atrial Fibrillation
Supraventricular Tachycardia
Non Cardiac:
Chronic Obstructive Pilmonary Disease
Pulmonary Embolism & Pulmonary Hypertension
Sepsis
Hypertension
Subarachnoid Haemorrhage
Renal Failure
Levels in health and disease can be affected by:
Age — increasing with increasing age
Gender — slightly higher in females
Obesity — levels are lower with increasing BMI.
Race — levels are higher in Caucasians compared with African Americans
Interpretation
Even in stable heart failure, there is a lot of within-person biological variability, i.e. a patient’s NT-proBNP result can change significantly from week to week without a significant change in clinical status. An increase or decrease of up to 98% of baseline may be seen due to this biological variation.
Generally it is not helpful to repeatedly measure NT-proBNP to monitor acute response to treatment. The test is expensive and should be dictated by clinical need and after consultation with a physician or cardiologist.
Test Method
Principle: 2-site Sandwich Immunoassay
Reagents: Siemens Atellica IM NT-proBNP
Analyser: Siemens Atellica IM
Limitations / Interference
Patient samples may contain heterophilic antibodies that could react in immunoassays to give falsely elevated or depressed results.
Patients taking biotin supplements may lead to falsely depressed results with this assay.