ANALYTE REFERENCE RANGE CLINICAL SIGNIFICANCE OTHER
BUN
Creatinine
Uric acid
Ammonia
Nonprotein Nitrogen Compounds Clinical Chemistry Review 92
8–26 mg/dL
0.7–1.5 mg/dL
M: 3.5–7.2
F: 2.6-6 mg/dL
19–60 μg/dL
↑kidney disease
↓overhydration or liver disease
↑kidney disease
↑gout, renal failure, ketoacido-
sis, lactate excess, high
nucleoprotein diet, leukemia,
lymphoma, polycythemia
↓administration of ACTH, renal
tubular defects
↑liver disease, hepatic coma,
renal failure, Reye’s syndrome
Synthesized by liver from ammonia. Excreted by kidneys.
Urease reagent. Don’t use sodium fluoride, EDTA, citrate, or
ammonium heparin. Test isn’t sensitive. Dilute urine 1:20 or
1:50 & refrigerate or acidify.
Waste product from dehydration of creatine (mainly in
muscles). Jaffe’s reaction (alkaline picrate) is nonspecific.
Enzymatic methods are more specific. Tests aren’t sensitive.
Normal BUN: creatinine ratio = 12–20. Dilute urine 1:100.
Increased = risk of renal calculi & joint tophi. Uricase
method. EDTA & fluoride interfere. Adjust urine pH to
7.5–8 to prevent precipitation.
Produced in GI tract. High levels are neurotoxic. Collect in
EDTA or heparin. Serum may cause ↑levels as NH 3 is gener-
ated during clotting. Chill immediately. Analyze ASAP. Avoid
contamination from ammonia in detergents or water.
