A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # |
Cystine, Random Urine with Creatinine
Test CodeCPT Codes
82131, 82570
Includes
Preferred Specimen
Minimum Volume
Other Acceptable Specimens
Instructions
Do not thaw. Patient age is required for correct reference range.
Transport Temperature
Specimen Stability
Refrigerated: Unacceptable
Frozen: 60 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
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 FDA. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.
Setup Schedule
Report Available
Clinical Significance
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.