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Test Directory Cystine, Quantitative, Random Urine

Cystine, Quantitative, Random Urine

Test Summary

This quantitative test may be useful for evaluation of individuals with clinically suspected cystinuria, including those with symptoms of kidney stones or cystine crystals detected in urinalysis [1]. Although 24-hour urine testing is generally preferred for diagnostic evaluation and monitoring of cystinuria [2], random or first-morning void urine collection may be helpful for diagnosis when 24-hour urine collection is not feasible (eg, for young children) [3].

Cystinuria, an autosomal recessive genetic disorder that can cause kidney stones, is characterized by excessive excretion of cystine and dibasic amino acids in the urine. Around 1% to 2% of all kidney stones, and 6% to 8% of kidney stones in children, are caused by cystinuria [1]. Approximately 83% of patients with cystinuria who develop a kidney stone will have a recurrence within 5 years [1]. Common complications of cystinuria include chronic kidney disease and hypertension [1].

This test does not differentiate between free and bound cystine in patients taking cystine-binding thiol drugs [1]. This test alone is not sufficient to predict risk of kidney stones in individuals with cystinuria [1].

The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings.

References
1. Daga S, et al. Urology. 2021;149:70-75.
2. Williams JC Jr, et al. Urolithiasis. 2021;49(1):1-16.
3. Servais A, et al. Kidney Int. 2021;99(1):48-58.

Aliases

Specimen Collection

Special Instructions

N/A

Preferred Specimen

1.8 mL random urine collected in a sterile screw-cap container

Minimum Volume

0.6 mL

Instructions

Do not use preservatives. Urine with a pH <2.0 will be rejected.
Do not thaw. Patient age is required for correct reference range.

Patient Preparation

N/A

Storage

N/A

Transport Temperature

Frozen

Specimen Stability

Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen: 60 days

Limitations

N/A

Other Acceptable Specimens

Catheterized urine • First void clean catch urine • Random clean catch urine

Unacceptable Specimens

Received room temperature • Received refrigerated • pH <2.0

Order Code

CYSTNR

EPIC (Premier) Code

LAB3453

Includes

Creatinine

CPT Code

82131
82570

Billing Code

670248
670249

CPT Statement

Methodology

Liquid Chromatography/Mass Spectrometry (LC/MS)

FDA Status

This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics. It has not been cleared or approved by the U.S. Food and Drug Administration. The FDA has determined that such clearance or approval is not necessary. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.

Physician Attestation of Informed Consent

N/A

Testing Laboratory

Quest Diagnostics Nichols Institute
33608 Ortega Highway
San Juan Capistrano CA, 92675

Department

Reference Testing

Reference Range

Cystine

Pediatric (<18 Years)			3.2-12.6 mmol/mol creat
Adult			3.4-16.4 mmol/mol creat

Creatinine, Random Urine

0-6 Months	0.18-2.48 mmol/L
7-11 Months	0.18-2.74 mmol/L
1-2 Years	0.18-9.72 mmol/L
3-8 Years	0.18-11.49 mmol/L
9-12 Years	0.18-14.14 mmol/L
>12 Years	1.77-23.31 mmol/L

Setup Schedule / Expected Turnaround Time

Mornings; 2 days a week. Report available 4 - 9 days.