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Unit Code 800006:
B-Type Natriuretic Peptide (BNP), Plasma
Useful For
Aids in the diagnosis of CHF
The role of BNP in monitoring CHF therapy is under investigation.
Clinical Information
B-type natriuretic peptide (brain natriuretic peptide [BNP]) is a 32-
amino acid ringed peptide secreted by the heart to regulate blood
pressure and fluid balance. (1) BNP is stored in and secreted
predominantly from membrane granules in the heart ventricles and
is continuously released from the heart in response to both ventricle
volume expansion and pressure overload. (2)
The natriuretic peptide system and the renin-angiotensin system
counteract each other in arterial pressure regulation. When arterial
pressure decreases, the kidneys release renin, which activates
angiotensinogen resulting in increased peripheral resistance of the
arterioles, thus increasing atrial pressure.
The natriuretic peptides counteract the effects of rennin secretion,
causing a reduction of blood pressure and in extracellular fluid
volume (3). Both BNP and ANP (atrial natriuretic peptide) are
activated by atrial and ventricular distension due to increased
intracardiac pressure. These peptides have both natriuretic and
diuretic properties: they raise sodium and water excretion by
increasing the glomerular filtration rate and inhibiting sodium
reabsorption by the kidney.
The New York Heart Association (NYHA) developed a functional
classification system for congestive heart failure (CHF) consisting
of 4 stages based on the severity of the symptoms. Various studies
have demonstrated that circulating BNP concentrations increase
with the severity of CHF based on the NYHA classification. (4-6)
Reference Values
Males:
< or = 45 years: < or = 35 pg/mL
46 years: < or = 36 pg/mL
47 years: < or = 37 pg/mL
48 years: < or = 38 pg/mL
49 years: < or = 39 pg/mL
50 years: < or = 40 pg/mL
51 years: < or = 41 pg/mL
52 years: < or = 42 pg/mL
53 years: < or = 43 pg/mL
54 years: < or = 45 pg/mL
55 years: < or = 46 pg/mL
56 years: < or = 47 pg/mL
57 years: < or = 48 pg/mL
58 years: < or = 49 pg/mL
59 years: < or = 51 pg/mL
60 years: < or = 52 pg/mL
61 years: < or = 53 pg/mL
62 years: < or = 55 pg/mL
63 years: < or = 56 pg/mL
64 years: < or = 57 pg/mL
65 years: < or = 59 pg/mL
66 years: < or = 60 pg/mL
67 years: < or = 62 pg/mL
68 years: < or = 64 pg/mL
69 years: < or = 65 pg/mL
70 years: < or = 67 pg/mL
71 years: < or = 69 pg/mL
72 years: < or = 70 pg/mL
73 years: < or = 72 pg/mL
74 years: < or = 74 pg/mL
75 years: < or = 76 pg/mL
76 years: < or = 78 pg/mL
77 years: < or = 80 pg/mL
78 years: < or = 82 pg/mL
79 years: < or = 84 pg/mL
80 years: < or = 86 pg/mL
81 years: < or = 88 pg/mL
82 years: < or = 91 pg/mL
> or = 83 years: < or = 93 pg/mL
Females:
< or = 45 years: < or = 64 pg/mL
46 years: < or = 66 pg/mL
47 years: < or = 67 pg/mL
48 years: < or = 69 pg/mL
49 years: < or = 71 pg/mL
50 years: < or = 73 pg/mL
51 years: < or = 74 pg/mL
52 years: < or = 76 pg/mL
53 years: < or = 78 pg/mL
54 years: < or = 80 pg/mL
55 years: < or = 82 pg/mL
56 years: < or = 84 pg/mL
57 years: < or = 87 pg/mL
58 years: < or = 89 pg/mL
59 years: < or = 91 pg/mL
60 years: < or = 93 pg/mL
61 years: < or = 96 pg/mL
62 years: < or = 98 pg/mL
63 years: < or = 101 pg/mL
64 years: < or = 103 pg/mL
65 years: < or = 106 pg/mL
66 years: < or = 109 pg/mL
67 years: < or = 112 pg/mL
68 years: < or = 114 pg/mL
69 years: < or = 117 pg/mL
70 years: < or = 120 pg/mL
71 years: < or = 123 pg/mL
72 years: < or = 127 pg/mL
73 years: < or = 130 pg/mL
74 years: < or = 133 pg/mL
75 years: < or = 137 pg/mL
76 years: < or = 140 pg/mL
77 years: < or = 144 pg/mL
78 years: < or = 147 pg/mL
79 years: < or = 151 pg/mL
80 years: < or = 155 pg/mL
81 years: < or = 159 pg/mL
82 years: < or = 163 pg/mL
> or = 83 years: < or =167 pg/mL
Interpretation
> normal < 200 pg/mL: likely compensated CHF
> or = 200 < or = 400 pg/mL: likely moderate CHF
> 400 pg/mL: likely moderate to severe CHF
BNP levels are loosely correlated with NYHA functional class
(see Table).
Table: Interpretive Levels for CHF
Functional Class 5th to 95th Percentile Median
I 15 to 499 pg/mL 95 pg/mL
II 10 to 1080 pg/mL 222 pg/mL
III 38 to >1300 pg/mL 459 pg/mL
IV 147 to >1300 pg/mL 1006 pg/mL
All CHF 22 to >1300 pg/mL 360 pg/mL
Elevation in BNP can occur due to right heart failure with cor
pulmonale (200-500 pg/mL), pulmonary hypertension (300-500
pg/mL), and acute pulmonary embolism (150-500 pg/mL).
Elevations also occur in patients with acute coronary syndromes.
Cautions
Lack of elevations have been reported if CHF is very acute (first
hour) or with ventricular inflow obstruction (hypertrophic obstructive
cardiomyopathy, mitral stenosis, atrial myxoma).
Some patients who have been exposed to animal antigens, either
in the environment or as part of treatment or imaging procedures,
may have circulating anti animal antibodies present. These anti-
bodies may interfere with the assay reagents to produce unreliable
results.
Clinical Reference
1. Krishnaswamy P, Lubien E, Clopton P, et al: Utility of B-natriuretic
peptide as a rapid, point-of-care test for screening patients
undergoing echocardiography to determine left ventricular
dysfunction. Am J Med 2001;111(4):274-279
2. McNairy M, Gardetto N, Clopton P, et al: Stability of B-type
natriuretic peptide levels during exercise in patients with congestive
heart failure: implications for outpatient monitoring with B-type
natriuretic peptide. Am Heart J 2002 March;143(3):406-411
3. Redfield MM, Rodeheffer RJ, Mahoney DW, et al: What is a normal
BNP? - a community-based study employing two assays for measure-
ment of BNP. J Card Fail 2001 September;7(3):30
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