Natriuretic peptides are lower than expected in obesity, so a normal value in a heavy, breathless patient does not rule heart failure out as firmly as it does in a lean one. They run higher in atrial fibrillation, in CKD and with advancing age, so a moderately raised value in these patients is less specific.
The practical response is not to abandon the test but to read it in context: lower the threshold for echocardiography in obesity, and in AF or CKD look for the trend and the echo findings rather than a single number.
- In obesity, a normal NT-proBNP does not exclude heart failure if symptoms fit.
- In AF, CKD and older age, expect higher baseline values and interpret a mild rise cautiously.
- Compare with the patient's own previous values where available.
- Use echocardiography to settle the diagnosis when the peptide and the picture disagree.
Why it matters
A single cut-off misleads most in exactly the patients most likely to have HFpEF.
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