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Test Code BUN Blood Urea Nitrogen (BUN) LAB140

Performing Laboratory

UnityPoint The Finley Hospital

Test Method

Enzymatic; Roche cobas Pro

Performance

Testing is performed Monday through Sunday.

Routine orders: Typically completed within 4 hours.

STAT orders: Typically completed within 30 minutes after the specimen arrives at the testing site.

Specimen Requirement

  1. Lithium heparin plasma (Green) is the specimen of choice. 0.5mL
  2. Serum (Red/Gold) and EDTA plasma (Purple) are also acceptable sample types.
  3. It is recommended that the serum or plasma be separated from contact with cells within 2 hours from time of collection.
  4. BUN blood specimens are stable for 7 days at 20-25°C, 7 days at 2-8°C, and 1 year at -20°C.

Useful For

Urea is the major end product of protein nitrogen metabolism. It is synthesized by the urea cycle in the liver from ammonia which is produced by amino acid deamination. Urea is excreted mostly by the kidneys but minimal amounts are also excreted in sweat and degraded in the intestines by bacterial action.

Determination of blood urea nitrogen is the most widely used screening test for renal function. When used in conjunction with serum creatinine determinations it can aid in the differential diagnosis of the three types of azotemia: prerenal, renal and postrenal. Elevations in blood urea nitrogen concentration are seen in inadequate renal perfusion, shock, diminished blood volume (prerenal causes), chronic nephritis, nephrosclerosis, tubular necrosis, glomerular nephritis (renal causes) and urinary tract obstruction (postrenal causes). Transient elevations may also be seen during periods of high protein intake. Unpredictable levels occur with liver diseases.

Reference Values

  1. Males: 
    1-17 years of age: 7-20 mg/dL
    ≥18 years of age: 8-24 mg/dL
    Reference values have not been established for patients <12 months of age.
  2. Females:
    1-17 years of age: 7-20 mg/dL
    ≥18 years of age: 6-21 mg/dL
    Reference values have not been established for patients <12 months of age. 

CPT Code Information

84520 Chemistry: Urea Nitrogen (Blood); Urea nitrogen;
quantitative

LOINC Code Information

3094-0 Urea nitrogen