Sign in →

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

Reporting Name

Cystinuria Profile, QN, 24 hour

Useful For

Diagnosis of cystinuria

Specimen Type

Urine


Necessary Information


24-Hour volume is required.

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 toluene 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 in Special Instructions for multiple collections.


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Frozen (preferred) 70 days
  Refrigerated  14 days

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

Day(s) Performed

Monday through Friday

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

LOINC Code Information

Test ID Test Order Name Order LOINC Value
CYSQN Cystinuria Profile, QN, 24 hour In Process

 

Result ID Test Result Name Result LOINC Value
TM38 Collection Duration 13362-9
VL36 Urine Volume 3167-4
3583 Cystine 13966-7
3589 Lysine 25464-9
3590 Ornithine 25491-2
3591 Arginine 25322-9
50447 Reviewed By 18771-6

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, 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 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.

Interpretation

Homozygotes or compound heterozygotes with cystinuria excrete large amounts of cystine in urine, but the amount varies markedly. Urinary excretion of other dibasic amino acids (arginine, lysine, and ornithine) is also typically elevated. Plasma concentrations are generally normal or slightly decreased.

 

Individuals who are homozygous and heterozygous for nontype I cystinuria can be distinguished by the pattern of urinary amino acids excretion: homozygous individuals secrete large amounts of cystine and all 3 dibasic amino acids, whereas heterozygous individuals secrete more lysine and cystine than arginine and ornithine.

Clinical Reference

1. Saravakos P, Kokkinou V, Giannatos E: Cystinuria. Current Diagnosis and Management. Urology April 2014;4(83):693-699

2. Palacin, M, Goodyer, P, Nunes V, Gasparini P: Cystinuria. Edited by D Valle, AL Beaudet, B Vogelstein, et al. New York, McGraw-Hill, 2014. Accessed 6 July 2016. Available at http://ommbid.mhmedical.com/content.aspx?sectionid=62653976&bookid=971&Resultclick=2

Report Available

3 to 5 days

Method Name

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

Urine Preservative Collection Options

Note: The addition of preservative or application of temperature controls must occur within 4 hours of completion of the collection.

Ambient

No

Refrigerate

OK

Frozen

OK

50% Acetic Acid

No

Boric Acid

No

Diazolidinyl Urea

No

6M Hydrochloric Acid

No

6M Nitric Acid

No

Sodium Carbonate

No

Thymol

No

Toluene

Preferred

Forms

If not ordering electronically, complete, print, and send an Inborn Errors of Metabolism Test Request (T798) with the specimen. 

Mayo Clinic Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

mml-biochemical