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Test Code RURCU Uric Acid, Random, Urine

Reporting Name

Uric Acid, Random, U

Useful For

Differentiation of acute uric acid nephropathy from other causes of acute renal failure

 

Patients who cannot collect a 24-hour specimen, typically small children, a uric acid to creatinine ratio can be used to approximate 24-hour excretion

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type

Urine


Specimen Required


Container/Tube: Plastic, 5-mL tube (T465)

Specimen Volume: 4 mL

Collection Instructions:

1. Collect a random urine specimen.

2. No preservative.

Additional Information: A timed 24-hour urine collection is usually the preferred specimen for measuring and interpreting this urinary analyte. Random collections normalized to urinary creatinine may be of clinical use in the following 2 scenarios:

1. In patients who cannot collect a 24-hour specimen, typically small children, a uric acid to creatinine ratio can be used to approximate 24-hour excretion.

2. When acute renal failure secondary to uric acid is suspected, a uric acid to creatinine ratio (mg/mg) >1.0 is consistent with acute uric acid nephropathy, whereas values <0.75 are consistent with other causes of acute renal failure.(1)


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
Urine Refrigerated (preferred) 14 days
  Frozen  14 days

Reference Values

No established reference values

Day(s) and Time(s) Performed

Monday through Sunday; Continuously

Test Classification

This test has been cleared or approved by the U.S. 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

84560

LOINC Code Information

Test ID Test Order Name Order LOINC Value
RURCU Uric Acid, Random, U In Process

 

Result ID Test Result Name Result LOINC Value
URCO2 Uric Acid, Random, U 3086-6
CREA7 Creatinine Concentration 2161-8
RATO6 Uric Acid/Creatinine Ratio 3089-0

Clinical Information

Uric acid is the end-product of purine metabolism. It is freely filtered by the glomeruli and most is reabsorbed by the tubules. There is also active tubular secretion.

 

Increased levels of uric acid in the urine usually accompany increased plasma uric acid levels unless there is a decreased excretion of uric acid by the kidneys. Urine uric acid levels reflect the amount of dietary purines and also endogenous nucleic acid breakdown.

 

Acute uric acid nephropathy can cause acute renal failure due to uric acid precipitation within tubules. This is most commonly seen in patients with hematologic malignancies (eg, lymphoma, leukemia), often after acute lysis of cells by chemotherapy. Less commonly this may be seen with seizures, treatment of solid tumors, overproduction of uric acid in metabolic disorders such as Lesch-Nyhan syndrome or decreased uric acid reabsorption in the proximal nephron due to tubular disorder (Fanconi syndrome).

Interpretation

Uric acid excretion can be either decreased or increased in response to a variety of pharmacologic agents.

 

Urine uric acid levels are elevated in states of uric acid overproduction such as in leukemia and polycythemia and after intake of food rich in nucleoproteins.

 

A uric acid to creatinine ratio (mg/mg) >1.0 is consistent with acute uric acid nephropathy, whereas values <0.75 are consistent with other causes of acute renal failure.(1)

 

A timed 24-hour collection is usually the preferred method for measuring and interpreting this urinary analyte. Random collections normalized to urinary creatinine may be of clinical use in 2 scenarios, however:

-When acute renal failure secondary to uric acid is suspected, a uric acid to creatinine ratio (mg/mg) >1.0 is consistent with acute uric acid nephropathy, whereas values <0.75 are consistent with other causes of acute renal failure.(1)

-In patients who cannot collect a 24-hour specimen, typically small children, a uric acid creatinine ratio can be used to approximate 24-hour excretion.  

              

Pediatric Reference Ranges of Uric Acid/Creatinine (mg/mg)(2)

Age (year)

5th Percentile

95th Percentile

0-0.5

>1.189

<2.378

0.5-1

>1.040

<2.229

1-2

>0.743

<2.080

2-3

>0.698

<1.932

3-5

>0.594

<1.635

5-7

>0.446

<1.189

7-10

>0.386

<0.832

10-14

>0.297

<0.654

14-17

>0.297

<0.594

Clinical Reference

1. Kelton J, Kelley WN, Holmes EW: A rapid method for the diagnosis of acute uric acid nephropathy. Arch Intern Med 1978;138(4):612-615

2. Matos V, Van Melle G, Werner D et al: Urinary oxalate and urate to creatinine ratios in a healthy pediatric population. Am J Kidney Dis 1999; Aug;34(2):e1

3. Newman DJ, Price CP: Renal function and nitrogen metabolites. In Textbook of Clinical Chemistry. Edited by NW Tietz. Philadelphia, WB Saunders Company, 1999, pp 1245-1250

Analytic Time

Same day/1 day

Reject Due To

Hemolysis

NA

Lipemia

NA

Icterus

NA

Other

NA

Method Name

Uricase