BUN and Blood Urea Nitrogen (T502) [Back]
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| RISK ASSESSMENT VALUE: |
This test measures urea, the chief end product of protein metabolism which is formed in the liver and excreted by the kidneys. The BUN level reflects renal excretory capacity but is more sensitive to other factors such as state of hydration and protein intake so is a less reliable indicator of renal function than serum creatinine. Significant renal dysfunction can be expected to increase both values providing a highly specific risk indicator with fewer false positives than looking at just one value or the other. BUN may be a more sensitive indicator in the elderly because of loss of muscle mass that reduces creatinine formation. However, this disparity is limited mainly to those both old and sick who would typically be excluded from the insured population and specificity remains a problem.
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| NORMAL RESULTS: |
6 - 25 mg/dL
Values are a bit lower in babies and slightly higher in men than women. They are higher in the general population at age >60 but this may reflect higher levels of renal dysfunction secondary to hypertension, diabetes, etc.
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| ABNORMAL RESULTS: |
Elevated BUN especially in conjunction with elevated or borderline elevated creatinine values suggest decreased renal function from any cause.
Low BUN values can be present with severe liver disease but in the insurance setting are of little or no concern in isolation.
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| ADDITIONAL TESTS: |
None
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| SAMPLE NEEDED: |
Separated serum from a red-stopper tube
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| SAMPLE STABILITY: |
10 days at room temperature; 2 weeks when refrigerated; indefinitely when frozen
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| METHOD & INSTRUMENT: |
Urea is hydrolyzed by urease to form CO2 and ammonia. The ammonia then reacts with ketoglutarate and NADH to yield glutamate and NAD, Hitachi Modular
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| INTERFERING FACTORS: |
Highly hemolyzed samples cause increased BUN values.
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| PURPOSE: |
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| PROFILE INCLUDES: |
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| RISK RANGE & UNITS: |
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