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HelpTest ID CYSQN Cystinuria Profile, Quantitative, 24 Hour, Urine
Necessary Information
1. 24-Hour volume (in milliliters) is required.
2. Patient's age is required.
3. Include family history, clinical condition (asymptomatic or acute episode), diet, and drug therapy information.
Specimen Required
Supplies: Urine Tubes, 10 mL (T068)
Specimen Volume: 5 mL
Collection Instructions:
1. Collect before intravenous pyelogram.
2. Collect urine for 24 hours.
3. Add 20 mL of toluene as preservative at start of collection. If preservative is not available, refrigerate during collection.
4. Mix well before taking 5-mL aliquot.
Additional Information: See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens for multiple collections.
Forms
If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.
Useful For
Diagnosis of cystinuria
Special Instructions
Method Name
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Reporting Name
Cystinuria Profile, QN, 24 hourSpecimen Type
UrineSpecimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | |
|---|---|---|---|
| Urine | Frozen (preferred) | 70 days | |
| Refrigerated | 14 days |
Clinical Information
Cystinuria is an inborn error of metabolism resulting from poor absorption and reabsorption of the amino acid cystine in the intestines and kidneys. This leads to an accumulation of poorly soluble cystine in the urine and results in the production of kidney stones (urolithiasis). Symptoms may include acute episodes of abdominal or lower back pain and the presence of blood in the urine (hematuria). Recurrent episodes of kidney stones may result in frequent urinary tract infections, which may ultimately result in renal insufficiency. The combined incidence of cystinuria has been estimated to be 1 in 7000.
Cystinuria is an autosomal recessive disease, but some heterozygous carriers have an autosomal dominant, incomplete penetrance appearance with elevated, but typically nondisease-causing, urinary cystine excretion. Cystinuria is caused by variants in genes, SLC3A1 on chromosome 2p and SLC7A9 on chromosome 19q. Initially, the disease was classified into subtypes I, II, and III (type II and III are also referred as nontype-I) based on the amount of urinary cystine excreted in heterozygous parental specimens. A new classification system has been proposed to distinguish the various forms of cystinuria: type A, due to variants in the SLC3A1 gene; type B, due to variants in the SLC7A9 gene; and type AB, due to 1 variant in each SLC3A1 and SLC7A9 gene.
Reference Values
CYSTINE
3-15 years: 11-53 mcmol/24 h
≥16 years: 28-115 mcmol/24 h
LYSINE
3-15 years: 19-140 mcmol/24 h
≥16 years: 32-290 mcmol/24 h
ORNITHINE
3-15 years: 3-16 mcmol/24 h
≥16 years: 5-70 mcmol/24 h
ARGININE
3-15 years: 10-25 mcmol/24 h
≥16 years: 13-64 mcmol/24 h
Conversion Formulas:
Result in mcmol/24 hours x 0.24=result in mg/24 h
Result in mg/24 hours x 4.17=result in mcmol/24 h
Cautions
No significant cautionary statements
Day(s) Performed
Monday through Friday
Report Available
3 to 5 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
82136