Unit Converter
NT‐proBNP (N-terminal pro B-type natriuretic peptide)

SI UNITS (recommended)

CONVENTIONAL UNITS

Synonyms

  • NT-proBNP
  • N-terminal pro–BNP
  • N-proBNP
  • ProBNP (1–76 fragment)
  • Inactive BNP fragment
  • Natriuretic peptide precursor fragment

Units of Measurement

  • pmol/L
  • pg/mL
  • pg/dL
  • pg/100 mL
  • pg%
  • pg/L
  • ng/L

Molecular Weight

~8.5 kDa (76–amino-acid inactive peptide)

Unit Conversions

Mass ↔ Molar

Molecular weight = 8500 g/mol

1 pmol/L=8.5 pg/mL1\ \text{pmol/L} = 8.5\ \text{pg/mL}1 pmol/L=8.5 pg/mL 1 pg/mL=0.1176 pmol/L1\ \text{pg/mL} = 0.1176\ \text{pmol/L}1 pg/mL=0.1176 pmol/L

pg/mL ↔ ng/L

1 pg/mL=1 ng/L1\ \text{pg/mL} = 1\ \text{ng/L}1 pg/mL=1 ng/L

pg/dL

1 pg/mL=100 pg/dL1\ \text{pg/mL} = 100\ \text{pg/dL}1 pg/mL=100 pg/dL

Description

NT-proBNP is the inactive peptide fragment released from cleavage of proBNP into:

  • BNP (active hormone, 32 aa)
  • NT-proBNP (inactive, 76 aa)

NT-proBNP is:

  • More stable in blood
  • Has longer half-life (60–120 minutes)
  • Less affected by rapid physiologic changes

This makes it a superior biomarker for:

  • Heart failure diagnosis
  • Risk assessment
  • Monitoring treatment
  • Prognosis determination

Released in response to:

  • Increased myocardial wall stress
  • Ventricular stretch
  • Pressure or volume overload

Physiological Role

Although inactive, NT-proBNP reflects the activation of the natriuretic peptide system, which promotes:

  • Natriuresis
  • Vasodilation
  • Inhibition of RAAS
  • Reduction in cardiac preload & afterload

Clinical Significance

HIGH NT-proBNP

1. Heart Failure (Primary Use)

Elevated in:

  • Acute decompensated HF
  • Chronic HF
  • Left ventricle systolic/diastolic dysfunction

Diagnostic Thresholds (ESC & ACC Guidelines)

Rule-out of HF (Acute):

  • NT-proBNP < 300 pg/mL → Acute HF very unlikely

Age-stratified rule-in thresholds (Acute):

  • < 50 years → >450 pg/mL
  • 50–75 years → >900 pg/mL
  • 75 years → >1800 pg/mL

Chronic HF (non-acute):

  • >125 pg/mL → strongly suggests HF

2. Other Causes of Elevated NT-proBNP

  • Pulmonary embolism
  • Pulmonary hypertension
  • Atrial fibrillation
  • Sepsis
  • Renal failure (reduced clearance)
  • ACS / myocardial ischemia
  • Stroke / subarachnoid hemorrhage
  • Severe anemia
  • Cirrhosis
  • Severe COPD exacerbation

LOW NT-proBNP

Usually excludes HF in symptomatic patients.

Clinical meaning

  • NT-proBNP < 300 pg/mL (acute dyspnea) strongly rules out heart failure
  • Very low levels in obese patients due to reduced natriuretic peptide secretion

Reference Intervals

Normal (General Population)

  • < 125 pg/mL (chronic)
  • < 300 pg/mL (acute settings)

Age-Adjusted Normal (ESC)

AgeNormal Upper Limit
<50 years<300 pg/mL
50–75 years<450 pg/mL
>75 years<900 pg/mL

Severe HF Indicators

  • >5000 pg/mL → high mortality risk
  • >10,000 pg/mL → advanced decompensated HF

Diagnostic Uses

1. Diagnosis of Heart Failure

Best biomarker for:

  • Acute HF in emergency
  • Chronic HF in outpatient settings

2. Prognosis

Higher NT-proBNP = poorer survival in:

  • HF
  • ACS
  • Pulmonary hypertension

3. Treatment Monitoring

Levels fall with:

  • Diuretics
  • ACE inhibitors
  • ARNI (sacubitril/valsartan)
  • Beta-blockers

4. Differentiating Dyspnea

Helps distinguish:

  • HF vs COPD
  • HF vs pneumonia

5. Renal Disease

Interpreted cautiously because reduced clearance elevates values.

Analytical Notes

  • Sample: plasma (EDTA preferred)
  • Stable for hours; more stable than BNP
  • Renal dysfunction → falsely elevated
  • Obesity → falsely low
  • Avoid hemolysis and delays in processing

Clinical Pearls

  • NT-proBNP <300 pg/mL rules out acute heart failure better than ECG or chest X-ray.
  • Obese patients may have low NT-proBNP despite HF - interpret carefully.
  • Serial NT-proBNP measurements reflect treatment response.
  • Markedly high levels (>10,000 pg/mL) occur in severe HF and renal failure.
  • BNP and NT-proBNP are both valid, but NT-proBNP is more stable.

Interesting Fact

The hormone BNP was originally extracted from porcine brain tissue, which is why it is called “Brain Natriuretic Peptide”-even though the heart produces most of it.

References

  1. Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Cardiac Markers
  2. ESC 2021 Heart Failure Guidelines
  3. ACC/AHA Heart Failure Guidelines
  4. Mayo Clinic Laboratories - NT-proBNP
  5. ARUP Consult - Natriuretic Peptide Testing
  6. MedlinePlus / NIH - BNP/NT-proBNP Testing

Last updated: January 26, 2026

Reviewed by : Medical Review Board

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