NT-proBNP Unit Converter
NT-proBNP Unit Converter
Convert NT-proBNP between pg/mL, ng/L and pmol/L, with age-stratified thresholds and why it is the marker to trend on sacubitril/valsartan.
NT-proBNP converter
Mass ⇄ molarNT-proBNP 1200 pg/mL
Formula and conversion factor
pg/mL = pmol/L ÷ 0.1182
- 0.1182
- derived from the molecular weight of NT-proBNP, the inactive 76-amino-acid fragment, 8457.5 Da
- ng/L
- numerically identical to pg/mL
- renal clearance
- NT-proBNP is cleared predominantly by the kidney, unlike BNP, so it is more affected by renal function
Worked example
NT-proBNP 1200 pg/mL
1200 × 0.1182 = 141.8 pmol/L
= 1200 ng/L, numerically identical to pg/mL
Age-stratified rule-in thresholds (acute breathlessness)
| Age | Rule-in threshold |
|---|---|
| Under 50 | 450 pg/mL |
| 50 – 75 | 900 pg/mL |
| Over 75 | 1800 pg/mL |
Why NT-proBNP behaves differently from BNP
NT-proBNP is the inactive amino-terminal fragment cleaved from proBNP alongside the active hormone, and it is cleared predominantly by the kidney rather than through the neprilysin pathway that clears BNP itself. That renal clearance means NT-proBNP is more affected by kidney function than BNP, and a reduced eGFR should be accounted for before treating a raised result as purely cardiac in origin.
Its longer half-life gives more stable measurements than BNP, and interpretation uses age-adjusted thresholds rather than a single cut-off. In acute breathlessness the rule-in thresholds rise with age — 450 pg/mL under 50, 900 pg/mL from 50 to 75, and 1800 pg/mL over 75 — reflecting the fact that both cardiac stiffening and declining renal clearance push the baseline upward with age. Rule-out sits at 300 pg/mL in the acute setting and 125 pg/mL in the non-acute setting. The same confounders as BNP apply beyond that: levels rise with age, atrial fibrillation and renal impairment, and are lowered by obesity, so a normal result in a markedly obese patient still needs cautious interpretation.
The one point where NT-proBNP diverges sharply from BNP is sacubitril/valsartan. Because NT-proBNP is not a neprilysin substrate, it is unaffected by the drug and continues to fall as heart failure improves, while BNP itself rises on treatment. This is why NT-proBNP, not BNP, is the marker to follow in any patient established on the drug.
Frequently asked questions
How do I convert NT-proBNP from pg/mL to pmol/L?
Multiply by 0.1182. An NT-proBNP of 1200 pg/mL is 141.8 pmol/L. pg/mL and ng/L are numerically identical, so no conversion is needed between those two.
Why does NT-proBNP use age-stratified thresholds?
Both cardiac stiffening and declining renal clearance raise the baseline with age, so a single cut-off would be too sensitive in the young and too specific in the old. Acute rule-in thresholds are 450, 900 and 1800 pg/mL for under 50, 50 to 75, and over 75 respectively.
Is NT-proBNP more affected by kidney function than BNP?
Yes. NT-proBNP is cleared predominantly by the kidney, while BNP is cleared largely through neprilysin degradation, so reduced eGFR raises NT-proBNP more than it raises BNP.
Why is NT-proBNP preferred in patients on sacubitril/valsartan?
The drug inhibits neprilysin and raises BNP as a direct pharmacological effect, unrelated to disease activity. NT-proBNP is not a neprilysin substrate and continues to track heart failure status accurately.
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References
- McDonagh TA 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 et al. NT-proBNP testing for diagnosis and short-term prognosis in acute destabilized heart failure: an international pooled analysis. JAMA. 2005;293(6):1652–3400.
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.