NT-proBNP Heart Failure Interpreter
NT-proBNP Heart Failure Interpreter
Read an NT-proBNP against the right threshold for the setting and the patient's age: 300 pg/mL to rule out acute heart failure, 450, 900 or 1,800 to rule it in, and 125 in the outpatient clinic. Obesity lowers the number; kidney disease and atrial fibrillation raise it.
NT-proBNP Heart Failure
Value + age + setting → bandNT-proBNP 700 pg/mL in a 68-year-old presenting acutely with breathlessness
The thresholds
Rule out: NT-proBNP below 300 pg/mL, at any age
Rule in: 450 pg/mL under 50 · 900 pg/mL from 50 to 75 · 1,800 pg/mL over 75
Non-acute, outpatient
125 pg/mL (BNP 35 pg/mL) — above this, arrange echocardiography
- one rule-out, three rule-ins
- the rule-out threshold of 300 pg/mL works at every age, because a low value is a low value. The rule-in threshold has to rise with age, because NT-proBNP rises with age in people who do not have heart failure
- pg/mL = ng/L
- numerically identical, so no conversion is needed between the two units this assay is reported in
- obesity lowers it
- and this is the caveat that most often causes harm, because it runs in the reassuring direction. A normal NT-proBNP in a very obese patient is much weaker evidence against heart failure than the same value in a lean one, and the best cut-off in severe obesity is considerably lower
- renal impairment and atrial fibrillation raise it
- both independently, and both commonly. A raised value in someone with atrial fibrillation and an eGFR of 30 may be telling you about the rhythm and the kidneys rather than the ventricle
- sacubitril/valsartan
- inhibits neprilysin, which degrades BNP but not NT-proBNP. BNP therefore rises on treatment while NT-proBNP falls with clinical improvement, so NT-proBNP is the peptide to trend in anyone taking it
Worked example
NT-proBNP 700 pg/mL in a 68-year-old presenting acutely with breathlessness
700 is not below 300, so acute heart failure is not ruled out
At 68 years the age band is 50 to 75, so the rule-in threshold is 900 pg/mL
700 is below 900, so it is not ruled in either — this is the grey zone
Had the same patient been 78, the threshold would be 1,800 and 700 would still be grey. Had they been 45, the threshold would be 450 and 700 would rule in
The action is the same as it would have been without the test: examine, chest radiograph, echocardiogram. What the number has done is make heart failure worth actively excluding rather than assuming
If this patient has atrial fibrillation or an eGFR of 30, a value of 700 is even less informative — both raise NT-proBNP without heart failure
Which threshold applies when
| Setting | Purpose | Threshold |
|---|---|---|
| Acute breathlessness | Rule out acute heart failure | NT-proBNP below 300 pg/mL — at any age |
| Acute breathlessness, under 50 | Rule in acute heart failure | 450 pg/mL or above |
| Acute breathlessness, 50 to 75 | Rule in acute heart failure | 900 pg/mL or above |
| Acute breathlessness, over 75 | Rule in acute heart failure | 1,800 pg/mL or above |
| Non-acute, outpatient | Decide who needs echocardiography | 125 pg/mL (BNP 35 pg/mL) |
What moves NT-proBNP without heart failure
| Direction | Cause | Consequence for reading the result |
|---|---|---|
| Lowers | Obesity — and more so the higher the body mass index | A normal value is less reassuring. This is the caveat that causes harm, because it runs in the direction of false reassurance |
| Lowers | Flash pulmonary oedema sampled very early | The peptide may not have risen yet; treat the patient, not the number |
| Raises | Increasing age | Which is exactly why the acute rule-in thresholds are age-stratified |
| Raises | Chronic kidney disease and acute kidney injury | Reduced clearance plus genuine cardiac strain; interpret alongside eGFR |
| Raises | Atrial fibrillation | Substantially, and independently of ventricular function |
| Raises | Pulmonary embolism, pulmonary hypertension, valve disease | Right ventricular strain raises it as readily as left |
| Raises | Sepsis, severe anaemia, critical illness | Common in exactly the patients in whom heart failure is being considered |
| Neither | Sacubitril/valsartan | Raises BNP by inhibiting its breakdown but not NT-proBNP, so NT-proBNP is the peptide to trend on this drug |
A very good rule-out, a mediocre rule-in, and a grey zone in between
NT-proBNP is the inactive fragment released in equal amounts with BNP when the ventricle is stretched, and it is the more stable of the two in the sample tube. Its outstanding property is how well it rules acute heart failure out. In an acutely breathless patient, a value below 300 pg/mL carries a negative predictive value close to 99 per cent, and that single threshold works at every age. Ruling in is harder, because NT-proBNP rises with age in people who do not have heart failure at all, which is why the rule-in threshold is stratified: 450 pg/mL under 50, 900 from 50 to 75, and 1,800 over 75.
The setting matters as much as the number. Those figures are for acute breathlessness. In the outpatient clinic, where the question is whether someone with gradual exertional symptoms should have an echocardiogram, the threshold is 125 pg/mL for NT-proBNP and 35 pg/mL for BNP. Carrying the acute rule-out of 300 into a clinic misses chronic heart failure in everyone between 125 and 300; carrying the clinic threshold of 125 into an emergency department refers almost every breathless patient for urgent echocardiography. Both errors are common.
Three confounders change how a result should be read, and the first is the one that causes harm. Obesity lowers natriuretic peptides, so an obese patient can have a normal NT-proBNP while volume overloaded, and the best cut-off in severe obesity is considerably lower than the standard one. Because that error runs in the reassuring direction, it is the one most likely to end in a missed diagnosis. In the other direction, chronic kidney disease and atrial fibrillation both raise NT-proBNP substantially and independently of ventricular function, as do pulmonary embolism, pulmonary hypertension, valve disease, sepsis and severe anaemia — all of which can also coexist with heart failure rather than replace it as the explanation.
One drug interaction is worth knowing by itself. Sacubitril/valsartan inhibits neprilysin, the enzyme that degrades BNP. BNP therefore rises on treatment even as the patient improves, while NT-proBNP, which neprilysin does not cleave, falls with clinical improvement in the usual way. In anyone taking sacubitril/valsartan, NT-proBNP is the peptide to trend and a rising BNP is expected rather than alarming. Finally, none of these thresholds is a decision. A patient below 300 pg/mL who looks like they are in heart failure needs examining again; a patient above 1,800 who has atrial fibrillation and an eGFR of 25 needs an echocardiogram before anyone concludes anything. The number changes the probability. The clinician makes the diagnosis.
Frequently asked questions
What NT-proBNP level rules out heart failure?
In acute breathlessness, a value below 300 pg/mL rules out acute heart failure with a negative predictive value close to 99 per cent, at any age. In the outpatient setting the threshold is lower — below 125 pg/mL makes chronic heart failure unlikely, and the corresponding BNP figure is 35 pg/mL.
What are the age-stratified NT-proBNP thresholds for acute heart failure?
For ruling acute heart failure in: 450 pg/mL or above under 50 years, 900 pg/mL or above from 50 to 75, and 1,800 pg/mL or above over 75. Only the rule-in threshold is age-stratified; the rule-out threshold of 300 pg/mL applies at every age.
Does obesity affect NT-proBNP?
Yes, and in the direction that causes harm — obesity lowers it. An obese patient can have a normal NT-proBNP while volume overloaded, and the best cut-off in severe obesity is considerably lower than the standard one. A normal result is therefore much weaker evidence against heart failure in a very obese patient than in a lean one.
Why is my NT-proBNP high if my heart is normal?
Several common conditions raise it independently of ventricular function: increasing age, chronic kidney disease, atrial fibrillation, pulmonary embolism, pulmonary hypertension, valve disease, sepsis and severe anaemia. A raised value means the peptide is up, not that heart failure is present — an echocardiogram is what settles it.
Should I use BNP or NT-proBNP on sacubitril/valsartan?
NT-proBNP. Sacubitril inhibits neprilysin, which degrades BNP but has no effect on the cleavage of NT-proBNP, so BNP rises on treatment even as the patient improves. NT-proBNP still falls with clinical improvement and is the peptide to trend in anyone taking the drug.
What does a result in the grey zone mean?
That the test has not answered the question. Between 300 pg/mL and the age-stratified rule-in threshold, acute heart failure is neither excluded nor established. The next steps are clinical — examination, chest radiograph and echocardiography — rather than a repeat measurement.
Related calculators
References
- McDonagh TA, Metra M, Adamo M, et al. 2021 ESC Guidelines for the diagnosis and treatment of acute and chronic heart failure. Eur Heart J. 2021;42(36):3599–3726.
- Januzzi JL Jr, van Kimmenade R, Lainchbury J, et al. NT-proBNP testing for diagnosis and short-term prognosis in acute destabilized heart failure: an international pooled analysis of 1256 patients — the International Collaborative of NT-proBNP Study. Eur Heart J. 2006;27(3):330–337.
- Januzzi JL Jr, Chen-Tournoux AA, Christenson RH, et al. N-terminal pro-B-type natriuretic peptide in the emergency department: the ICON-RELOADED study. J Am Coll Cardiol. 2018;71(11):1191–1200.
- Mueller C, McDonald K, de Boer RA, et al. Heart Failure Association of the European Society of Cardiology practical guidance on the use of natriuretic peptide concentrations. Eur J Heart Fail. 2019;21(6):715–731.
- Bayes-Genis A, Docherty KF, Petrie MC, et al. Practical algorithms for early diagnosis of heart failure and heart stress using NT-proBNP: a clinical consensus statement from the Heart Failure Association of the ESC. Eur J Heart Fail. 2023;25(11):1891–1898.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.