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Test Code LAB450 Uric Acid, Urine, Timed

Performing Laboratory

St. Louis Children's Hospital Laboratory - Chemistry

Specimen Requirements

Patient Preparation: None

Collection Container/Tube:

Preferred: Plain, brown-orange 24-hour urine collection container without preservatives

Specimen Collection Volume: Entire urine specimen collected over timed period required

Submission Container/Tube: If specimen is coming from outside facility, mix well and measure total volume before making aliquot with a minimum of 5.0 mL of urine into a plastic, leak-proof, screw-capped tube for transport labeling with volume and duration times or send entire 24-hr urine jug.

Special Instructions: 

  1. Refrigerate specimen during collection
  2. Note collection start and stop dates and times on collection container
  3. Call lab at 314-454-4268 to obtain 24-hour collection jug if needed
  4. Follow instructions on "Urine Collection"

Sample Rejection

Mislabled or unlabeled specimens

Logistics

Test Availability: Monday-Sunday

Cut-off time: None, performed as received

Turnaround Time: Same Day; 2 hours from receipt in performing lab

Reference Values

Reference Interval: No reference intervals established

Critical Value: None established

 

Methodology

Enzymatic Colorimetric (Uricase)

Limitations

  • HIgh homogentisic acid concentrations in urine samples leads to false results.
  • Dicynone (Etamsylate) at therapeutic concentrations may lead to false-low results.
  • Calcium dobesilate, Levodopa, and methyldopa can all cause artificially low uric acid results.

Additional Information

FOR SLCH CORE LABORATORY USE ONLY

Lab Processing Instructions: Mix well and measure total volume collected. Prepare a 7-mL aliquot and check pH. If pH is <8 carefully add 6N NaOH in 1 drop increments until the pH is between 8-10. Do not over adjust.

Heat aliquot for 10 min at 56o C then spin and separate. Aliquot a sample of the cleared urine into a Roche-false bottom tube for testing. 

Processed Volume: minimum 0.3 mL urine

Analyte Stability:

Specimen Type Temperature    Time    
urine (without preservative)     Ambient 3 days  
  Refrigerated     3 days   
  Frozen  3 days     

 

NOTE: Total volume of specimen collected and collection duration period is required. Note this information on the aliquot container label and into LIS system

Test Classification and CPT Code

84560

LOINC

Uric Acid Ur:   3086-6

Volume Ur:      19153-6

Duration:         13362-9

Last Reviewed

07/2025