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HelpTest ID: CYSR Cystinuria Profile, Quantitative, Random, Urine
Reporting Name
Cystinuria Profile, QN, RandomUseful For
Biochemical diagnosis and monitoring of cystinuria
Specimen Type
UrineSpecimen 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) and Time(s) Performed
Monday through Friday; 9 a.m. and 1 p.m.
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
Analytic Time
3 days (not reported on Saturday or Sunday)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.
mml-biochemical