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Test Code LAB841 Uric Acid, Urine, 24 hour

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 24 hour period

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: 

<18 years: No established reference values                                               
≥ 18 years: 200-750 mg/24 hours

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
  • if collection duration is <18 hours or >30 hours cancel the 24Hr orderable and reorder test using the Timed orderable.

Test Classification and CPT Code

84560

LOINC

Uric Acid 24H:   3087-4

Volume Ur:        19153-6

Duration:           13362-9

Last Reviewed

07/2025