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Interpretive Handbook

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Test 83873 :
B-Type Natriuretic Peptide (BNP), Plasma

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

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 arterial pressure.

 

The natriuretic peptides counteract the effects of renin secretion, causing a reduction of blood pressure and in extracellular fluid volume.(3) Both BNP and atrial natriuretic peptide (ANP) 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)

Useful For Suggests clinical disorders or settings where the test may be helpful

Aids in the diagnosis of congestive heart failure (CHF)

 

The role of brain natriuretic peptide in monitoring CHF therapy is under investigation

Interpretation Provides information to assist in interpretation of the test results

>normal <200 pg/mL: likely compensated congestive heart failure (CHF)

> or =200 to < or =400 pg/mL: likely moderate CHF

>400 pg/mL: likely moderate-to-severe CHF

 

Brain natriuretic peptide (BNP) levels are loosely correlated with New York Heart Association (NYHA) functional class (see Table).

  

Interpretive Levels for CHF

Functional Class

5th to 95th Percentile

Median

I

15 to 499 pg/mL

95 pg/mL

II

10 to 1,080 pg/mL

222 pg/mL

III

38 to >1,300 pg/mL

459 pg/mL

IV

147 to >1,300 pg/mL

1,006 pg/mL

All CHF

22 to >1,300 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 Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Lack of elevations have been reported if congestive heart failure 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 antianimal antibodies present. These antibodies may interfere with the assay reagents to produce unreliable results.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

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

Clinical References Provides recommendations for further in-depth reading of a clinical nature

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 measurement of BNP. J Card Fail 2001 September;7(3):30


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