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Test ID: CYSR Cystinuria Profile, Quantitative, Random, Urine

Reporting Name

Cystinuria Profile, QN, Random

Useful For

Biochemical diagnosis and monitoring of cystinuria

Specimen Type

Urine


Specimen Required


Supplies: Urine Tubes, 10 mL (T068)

Specimen Volume: 2 mL

Collection Instructions: Collect a random urine specimen.


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

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

Reference Values

Urine Amino Acid Reference Values (nmol/mg creatinine)

Age Groups

 ≤12 Months

13-35 Months

3-6 Years

7-8 Years

9-17 Years

≥18 Years

(n=36)

(n=45)

(n=39)

(n=10)

(n=40)

(n=145)

Arginine

Arg

10-560

20-395

14-240

<134

<153

<114

Ornithine

Orn

<265

<70

<44

<17

<18

<25

Cystine

Cys

12-504

11-133

<130

<56

<104

10-98

Lysine

Lys

19-1988

25-743

14-307

17-276

10-240

15-271

 

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
CYSR Cystinuria Profile, QN, Random In Process

 

Result ID Test Result Name Result LOINC Value
23517 Arginine 13708-3
23516 Ornithine 13786-9
23514 Cystine 30065-7
23515 Lysine 13769-5
50416 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)

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