BNP (NT-proBNP)
Code:
BNP
Sample Type:
Serum (Gold Top)
Minimum volume: 1 mL
Ref Ranges/Units:
Gateshead patients:
>75 years 0-250 ng/L
60-74 years 0-100 ng/L
<60 years 0-50 ng/L
Sunderland and South Tyneside patients:
0-400 ng/L
400-2000 ng/L – refer for assessment and transthoracic echocardiography within 6 weeks
>2000 ng/L – refer for urgent assessment and transthoracic echocardiography within 2 weeks
Turnaround:
Same Day (60 minutes from receipt for Urgent Samples)
Stability:
3 days at 20‑25°C
6 days at 2‑8°C
24 months at ‑20°C
Freeze only once.
Special Precautions/Comments:
Additional Information:
B-type natriuretic peptide (BNP) is a vasoactive hormone which is synthesised and secreted by ventricles in response to cardiac stretch. BNP acts on the kidney to oppose the effect of the renin-angiotensin-aldosterone (RAAS) pathway to limit fluid overload. It does this by increasing the glomerular filtration rate (GFR) and natriuresis (loss of sodium and water).
Heart failure is when the heart cannot provide sufficient cardiac output, leading to reduced blood pressure, activation of the RAAS pathway and fluid overload. Increased levels of BNP are therefore seen in heart failure in an attempt to reverse this process. BNP is used as a rule-out test for heart failure, and patients with increased BNP are referred for echocardiogram. The level of BNP is also prognostic because it correlates with severity. However, BNP is not specific and can also be increased by other causes including acute coronary syndrome, tachycardia, renal dysfunction (GFR <60) and sepsis. BNP also increases with age.
N-terminal pro B-type natriuretic peptide (NT-proBNP) is an inactive pro-peptide which is produced in equimolar concentrations to BNP. NT-proBNP is much more stable than BNP and is therefore easier to measure.
South of Tyne & Wear Pathology Centre
