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Uric Acid

A quantitative analysis of urine uric acid levels may supplement serum uric acid testing when seeking to identify disorders that alter production or excretion of uric acid (such as leukemia, gout, and renal dysfunction).

The most specific laboratory method for detecting uric acid is spectrophotometric absorption after treatment of the specimen with the enzyme uricase.

Purpose

• To detect enzyme deficiencies and metabolic disturbances that affect uric acid production, such as gout.
• To help measure the efficiency of renal clearance and to determine the risk of stone formation.

Patient preparation

• Explain to the patient that this test measures the body's production and excretion of a waste product known as uric acid.
• Inform him that he needn't restrict food or fluids before the test.
• Tell him the test requires urine collection over a 24-hour period, and teach him the proper collection technique.

Procedure and posttest care

• Collect the patient's urine over a 24­hour period.
• Resume administration of medications withheld before the test.

Precautions

• Send the specimen to the laboratory immediately after the collection period.

Reference values

Abnormal findings

Elevated urine uric acid levels may result from chronic myeloid leukemia, polycythemia vera, multiple myeloma, early remission in pernicious anemia, lymphosarcoma and lymphatic leukemia during radiotherapy, or tubular reabsorption defects, such as Fanconi's syndrome and hepatolenticular degeneration (Wilson's disease).

Interfering factors

• Failure to send the sample to the laboratory immediately.
• Diuretics, pyrazinamide, salicylates, phenylbutazone, probenecid, and allopurinol (possible increase or decrease).