Uric Acid, 24-Hour Urine

CPT: 84560
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Test Details

Use

Look for hyperuricosuria in patients with renal calculus formation. Identification of overexcretors re: risks of stone formation, identification of genetic defects, influence of overexcretion on therapy of gout. Uric acid nephrolithiasis occurs in primary gout or in secondary hyperuricemia (eg, malignant diseases). Uric acid nephrolithiasis may complicate ulcerative colitis, Crohn's disease, and surgical jejunoileal bypass. Most subjects with uric acid stones do not have gout.1 Evaluate uric acid metabolism in gout.

Methodology

Uricase

Reference Interval

250−750 mg/24 hours

Additional Information

Even mild renal failure decreases uric acid excretion. Uric acid excretion is decreased with hypertension.

A young patient with acute gouty arthritis, uric acid stones, and any patient who excretes >1000 mg uric acid/24 hours, should be evaluated for HPRT deficiency.2 The uric acid:creatinine ratio has been used as a test for Lesch-Nyhan syndrome (HPRTase deficiency). Normal control patients 0.21−0.59; partial enzyme deficient group 0.62−2.00; complete enzyme deficiency 1.98−5.35.3

The ratio of uric acid:creatinine in morning samples of urine has been used as a test for detection of the Lesch-Nyhan syndrome, which is associated with virtually complete absence of activity of the enzyme hypoxanthine-guanine phosphoribosyltransferase. This ratio has also been applied to 24-hour urine samples from adult patients with gout for detection of partial deficiency of the same enzyme. The uric acid:creatinine ratio in the urine of normal control patients is reported to range from 0.21−0.59. Patients with gout exhibit ratios of 0.15−0.73, whereas those patients with hyperuricemia associated with another disorder such as leukemia or glycogen-storage disease have ratios of 0.25−1.77. The ratio is 0.27−0.58 for patients with nongouty arthritis. Patients with complete hypoxanthine-guanine phosphoribosyltransferase deficiency are reported to have urinary uric acid:creatinine ratios of 1.98−5.35, as compared to 0.62−2.00 for patients with gout accompanied by partial enzyme deficiency.

The ratio of uric acid:creatinine concentration on a random urine specimen has also been shown to be >1.0 in patients with acute renal failure secondary to acute uric acid nephropathy, but <1.0 in patients with acute renal failure resulting from other causes.

Specimen Requirements

Specimen

Urine (24-hour)

Volume

10 mL aliquot of entire collection

Minimum Volume

1 mL aliquot

Container

Plastic urine container, no preservative

Patient Preparation

Standard diet 24 hours prior to collection

Collection

Mix well.

Storage Instructions

Maintain specimen at room temperature or refrigerate.

Stability Requirements

Temperature

Period

Room temperature

14 days

Refrigerated

14 days

Frozen

14 days

Freeze/thaw cycles

Stable x3

Causes for Rejection

Improper labeling; use of preservative; pH <6

Clinical Information

Special Instructions

State urine volume on the request form.

Footnotes

1. Pak CY. Renal calculi. In: Wyngaarden JB, Smith LH Jr, eds. Cecil Textbook of Medicine. 18th ed, vol 1. Philadelphia, Pa: WB Saunders Co;1988:638-644.
2. Wilson JM, Young AB, Kelley WN. Hypoxanthine-guanine phosphoribosyltransferase deficiency. The molecular basis of the clinical syndromes. N Engl J Med. 1983 Oct 13; 309(15):900-910 (review). 6136913
3. Pesce AJ, Kaplan LA. Methods in Clinical Chemistry. St Louis, Mo: Mosby-Year Book Inc;1987: 32.

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
003418 Uric Acid, 24 hr Urine 012898 Uric Acid, Urine mg/dL 3086-6
003418 Uric Acid, 24 hr Urine 013300 Uric Acid, Urine 24hr mg/24 hr 3087-4

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The LOINC® codes are copyright © 1994-2017, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee. Permission is granted in perpetuity, without payment of license fees or royalties, to use, copy, or distribute the LOINC® codes for any commercial or non-commercial purpose, subject to the terms under the license agreement found at https://loinc.org/license/. Additional information regarding LOINC® codes can be found at LOINC.org, including the LOINC Manual, which can be downloaded at LOINC.org/downloads/files/LOINCManual.pdf