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HelpTest ID: CYSQN Cystinuria Profile, Quantitative, 24 Hour, Urine
Reporting Name
Cystinuria Profile, QN, 24 hourUseful For
Diagnosis of cystinuria using 24-hour urine collections
Specimen Type
UrineNecessary 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
-Urine Tubes, 10 mL (T068)
-Diazolidinyl Urea (Germall) 5.0 mL (T822)
Specimen Volume: 5 mL
Collection Instructions:
1. Collect before intravenous pyelogram.
2. Add 5 g of diazolidinyl urea (Germall) as preservative at start of collection. If preservative is not available, refrigerate during collection.
3. Collect urine for 24 hours.
4. Mix well before taking 5-mL aliquot.
Additional Information: See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens 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: ≤53 mcmol/24 h
≥16 years: ≤115 mcmol/24 h
Lysine
3-15 years: ≤140 mcmol/24 h
≥16 years: ≤290 mcmol/24 h
Ornithine
3-15 years: ≤16 mcmol/24 h
≥16 years: ≤70 mcmol/24 h
Arginine
3-15 years: ≤25 mcmol/24 h
≥16 years: ≤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
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. It has not been cleared or approved by the US 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 | 90785-7 |
| 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 |
Genetics Test Information
This test provides a biochemical diagnosis of cystinuria through the measurement of cystine, lysine, ornithine, and arginine.
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 the short arm of chromosome 2 and SLC7A9 on the long arm of chromosome 19. Initially, the disease was classified into subtypes I, II, and III (type II and III are also referred as non-type 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
Individuals who are homozygous or compound heterozygous for 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 non-type 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. Servais A, Thomas K, Strologo LD, et al. Cystinuria: clinical practice recommendation. Kidney Int. 2021;99(1):48-58
2. Palacin M, Goodyer P, Nunes V, Gasparini P. Cystinuria. In: Valle DL, Antonarakis S, Ballabio A, Beaudet AL, Mitchell GA, eds. The Online Metabolic and Molecular Bases of Inherited Disease. McGraw Hill; 2019. Accessed October 24, 2024. Available at https://ommbid.mhmedical.com/content.aspx?bookid=2709§ionid=225555540
Report Available
3 to 5 daysMethod Name
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Forms
If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.
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