BNP vs NT-proBNP
| Parameter | BNP | NT-proBNP |
|---|---|---|
| What it is | Active form of natriuretic peptide | Inactive cleavage fragment |
| Normal cut-off | <35 pg/mL | <125 pg/mL (<75 yrs); <450 (<75); <1800 (>75) |
| Half-life | ~20 minutes | ~1–2 hours (longer in renal failure) |
| Cleared by | Natriuretic peptide receptors | Kidneys |
| Renal failure effect | Less affected | Higher levels (use with caution) |
Interpreting NT-proBNP
| NT-proBNP Level | Interpretation |
|---|---|
| <125 pg/mL (age <75) | Heart failure unlikely — look for another cause |
| 125–2000 pg/mL | Possible heart failure — echocardiogram indicated |
| >2000 pg/mL | Heart failure very likely — urgent cardiology |
| >5000 pg/mL | Acute decompensated heart failure or ACS |
Also Useful in Acute DyspnoeaIn A&E, NT-proBNP rapidly differentiates cardiac breathlessness (elevated) from pulmonary (often normal). This avoids unnecessary investigations and guides treatment.
Causes of Elevated BNP Without Heart Failure
Renal failure, sepsis, pulmonary embolism, right heart strain from COPD, severe anaemia, atrial fibrillation. Always interpret in clinical context.
Is BNP the same as NT-proBNP?
They are derived from the same precursor (pro-BNP) but are different molecules. Both detect heart failure well; most labs use one or the other. They cannot be directly compared numerically.
Can BNP be normal in heart failure?
Very rarely. BNP/NT-proBNP has >95% sensitivity for symptomatic heart failure. However, in treated, well-compensated heart failure, levels may be low-normal.
Does obesity affect BNP?
Yes — obesity is associated with lower BNP levels. In obese patients, the threshold for diagnosing heart failure may need to be lower, as BNP may be falsely reassuring.
How is BNP used to monitor heart failure treatment?
Falling BNP during treatment suggests response. Persistently high BNP despite optimal therapy is a poor prognostic sign and may prompt escalation to specialist care.
Medical Disclaimer: This page is for general education only and does not replace professional medical advice. Always consult a qualified healthcare provider.