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Test ID BUN Blood Urea Nitrogen (BUN), Serum

Reporting Name

Bld Urea Nitrog (BUN), S

Useful For

Screening test for evaluation of kidney function

Specimen Type

Serum


Necessary Information


Patient's age and sex are required.



Specimen Required


Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions:

1. Serum gel tubes should be centrifuged within 2 hours of collection.

2. Red-top tubes should be centrifuged, and the serum aliquoted into a plastic vial within 2 hours of collection.


Specimen Minimum Volume

See Specimen Required

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 7 days
  Frozen  365 days

Reference Values

Males

1-17 years: 7-20 mg/dL

≥18 years: 8-24 mg/dL

Reference values have not been established for patients who are <12 months of age.

 

Females

1-17 years: 7-20 mg/dL

≥18 years: 6-21 mg/dL

Reference values have not been established for patients who are <12 months of age.

Day(s) Performed

Monday through Sunday

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

84520

Clinical Information

Urea is the final degradation product of protein and amino acid metabolism. In protein catabolism, the proteins are broken down to amino acids and deaminated. The ammonia formed in this process is synthesized to urea in the liver. This is the most important catabolic pathway for eliminating excess nitrogen in the human body.

 

Increased blood urea nitrogen (BUN) may be due to prerenal causes (cardiac decompensation, water depletion due to decreased intake and excessive loss, increased protein catabolism, and high protein diet), renal causes (acute glomerulonephritis, chronic nephritis, polycystic kidney disease, nephrosclerosis, and tubular necrosis), and postrenal causes (eg, all types of obstruction of the urinary tract, such as stones, enlarged prostate gland, tumors).

 

The determination of serum BUN currently is the most widely used screening test for the evaluation of kidney function. The test is frequently requested along with the serum creatinine test since simultaneous determination of these 2 compounds appears to aid in the differential diagnosis of prerenal, renal and postrenal hyperuremia.

Cautions

No significant cautionary statements.

Clinical Reference

Lamb EJ, Jones GRD: Kidney function tests. In: Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018:497-500

Method Description

This kinetic ultraviolet assay utilizes urease to cleave urea, forming ammonia and carbon dioxide. The ammonia formed then reacts with alpha-ketoglutarate and reduced nicotinamide adenine dinucleotide (NADH) in the presence of urease/glutamate dehydrogenase to yield glutamate and NAD(+). The decrease in absorbance, due to the consumption of NADH, is measured kinetically and is proportional to the amount of urea in the sample.(Package insert: Urea/BUN reagent, Roche Diagnostics, 12/2019)

Report Available

Same day/1 to 2 days

Reject Due To

Gross hemolysis OK

NY State Approved

Yes

Method Name

Photometric/Urease

Forms

If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.