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Test ID CYSQN Cystinuria Profile, Quantitative, 24 Hour, Urine

Useful For

Diagnosis of cystinuria

Method Name

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

Reporting Name

Cystinuria Profile, QN, 24 hour

Specimen Type

Urine

Container/Tube: Plastic, 10-mL urine tube (Supply 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 toluene is not available, refrigerate during collection.

4. Mix well before taking 5-mL aliquot.

Additional Information:

1. 24-Hour volume is required.

2. See Urine Preservatives in Special Instructions for multiple collections.

Forms: New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (Supply T576) is available in Special Instructions.

 

Urine Preservative Collection Options

Ambient

No

Refrigerated

Yes

Frozen

Yes

6N HCl

No

50% Acetic Acid

No

Na2CO3

No

Toluene

Preferred

6N HNO3

No

Boric Acid

No

Thymol

No

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
Urine Frozen 14 days

Clinical Information

Cystinuria is an inborn error of metabolism resulting from poor absorption and reabsorption of the amino acid cystine in the intestine and in the kidney. 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, presence of blood in the urine (hematuria), and 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 7,000.

 

Cystinuria can be classified into 3 subtypes based on the excretion of amino acids in the urine of heterozygotes (parents or children of affected individuals). Heterozygotes of type I excrete normal amounts of cystine, while those with types II and III present with slight to moderate excretion of cystine and other amino acids (lysine, arginine, and ornithine). All 3 subtypes are caused by mutations in only 2 genes, SLC3A1 on chromosome 2p and SLC7A9 on chromosome 19q. A new classification system has been proposed to distinguish the various forms of cystinuria: type A, due to mutations in the SLC3A1 gene; type B, due to mutations in the SLC7A9 gene; and type AB, due to 1 mutation in each SLC3A1 and SLC7A9.

Reference Values

CYSTINE

3-15 years: 11-53 mcmol/24 hours

≥16 years: 28-115 mcmol/24 hours

 

LYSINE

3-15 years: 19-140 mcmol/24 hours

≥16 years: 32-290 mcmol/24 hours

 

ORNITHINE

3-15 years: 3-16 mcmol/24 hours

≥16 years: 5-70 mcmol/24 hours

 

ARGININE

3-15 years: 10-25 mcmol/24 hours

≥16 years: 13-64 mcmol/24 hours

 

Conversion Formulas:

Result in mcmol/24 hours x 0.24=result in mg/24 hours

Result in mg/24 hours x 4.17=result in mcmol/24 hours

Cautions

No significant cautionary statements.

Day(s) Performed

Monday through Friday; 8 a.m.

Report Available

3 days (not reported on Saturday or Sunday)

Performing Laboratory

Mayo Medical Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

82136

NY State Approved

Conditional