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Test Code LAB387 Cystine, Quantitative, Urine

Performing Laboratory

St. Louis Children's Hospital - Metabolic Genetics 

Specimen Requirements

Patient Preparation: Collect before intravenous pyelogram

Container/Tube  
Random: A clean, plastic urine container(s) with no preservative.
Acceptable: Clean, screw-cap container with no preservative.
Collection Volume: 5.0 mL (minimum of 1.0 mL) urine.

Submission Container/Tube: If specimen is coming from outside facility aliquot a minimum of 1.0 mL of urine into a plastic screw-capped tube for transport.

Special Instructions:   See Urine Collection instructions

Sample Rejection

Specimens collected with preservative
Mislabeled or unlabeled specimens

Logistics

Day(s) Test Set Up: Monday-Friday
Cut-off time: Varies; batched once a day in a.m.
Turnaround Time: 1-3 days

Reference Values

<30 days: ≤65 mcmol/mmol creatinine
1 month-6 months: ≤45 mcmol/mmol creatinine
6 months-2 years: ≤30 mcmol/mmol creatinine
≥ 2 years: ≤0 mcmol/mmol creatinine                                           

See "Urine Amino Acids Reference Values"

Critical Values: None established
 

Methodology

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Limitations

  • NA

Additional Information

For SLCH Laboratory use only

Lab Processing Instructions:

  1. Mix specimen well and make two aliquot tubes.
  2. Aliquot one sample into a 10-mL plastic screw cap urine tube for Met. Gen. testing and freeze in MET. GEN. basket in freezer #1. 
  3. Aliquot a second sample for LUO urine creatinine testing. Give aliquot to the PRO bench and let them know they have a Met. Gen. specimen that needs to be frozen ASAP post analysis in freezer #1.
  4. Place the original collection container (with or without any remaining sample) in freezer #1.

NOTE: If specimen needs to be shared with UA bench, make sure they are aware that the specimen is shared, and original container needs to be placed in Met. Gen. basket in freezer #1.

 

Processed Volume: 5.0 mL (minimum 1.0 mL) urine

NO SPECIMEN SHOULD BE REJECTED FOR VOLUME. PLEASE CALL THE FLOOR TO NOTIFY THE NURSE THAT ADDITIONAL SPECIMEN IS NEEDED, SHOULD BE COLLECTED, AND SENT TO LAB TO ADD TO WHAT IS ALREADY COLLECTED. GIVE ALL SPECIMENS TO METABOLIC GENETICS TO DECIDE IF QNS.

 

Specimen Stability Information

Specimen Type     Temperature    Time   
Urine   Ambient NA
  Refrigerated     NA
  Frozen  NA 

 

Test Classification and CPT Code

82131
Test Classification: This test was developed and its performance characteristics determined by St. Louis Children's Hospital Clinical Laboratory. It has not been cleared or approved by the U.S. Food and Drug Administration.

LOINC

30065-7

Last Reviewed

08/2025