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Citric Acid, 24-hour Urine (with Creatinine) (UCIT)
Test CodeLAB377
Quest Code
4616
Alias/See Also
UCIT
CPT Codes
82507, 82570
Includes
CPT code 81050 may be added at an additional charge for volume measurement
Preferred Specimen
10 mL aliquot of 24-hour urine collection
Minimum Volume
1.5 mL
Instructions
Do not include first morning specimen; collect all subsequent voidings. The last sample collected should be the first morning specimen voided the following morning at the same time as the previous morning's first voiding. Specify 24-hour total volume on container and test requisition.
Transport Container
Plastic leak-proof urine container
Transport Temperature
Refrigerated (cold packs)
Specimen Stability
Room temperature: 8 hours
Refrigerated: 30 days
Frozen: 60 days
Refrigerated: 30 days
Frozen: 60 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Received room temperature • Acidified urine
Methodology
Spectrophotometry (SP)
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
Tuesday and thursday
Reference Range
See Laboratory Report
Clinical Significance
This quantitative citric acid test, performed with a 24-hour urine specimen, may help assess the risk of calcium stone formation in the kidneys and inform patient management [1]. In general, 24-hour urine specimens are preferred to random urine specimens when measuring citric acid for diagnostic evaluation and monitoring of calcium nephrolithiasis [2]. Because daily urine excretion of creatinine fluctuates little, creatinine excretion can help determine if 24-hour urine specimens for citric acid have been completely and accurately collected [1].
Citrate inhibits calcium stone formation by binding and solubilizing calcium, which reduces supersaturation of calcium salts [1-2]. Approximately half of the patients with calcium stones have decreased urinary citrate levels [1]. Citrate is among several substances routinely screened to evaluate the risk of forming kidney stones. Low urinary citrate levels may indicate oral citrate treatment in patients with recurrent calcium nephrolithiasis [1]. Other conditions that can cause hypocitraturia include distal renal tubular acidosis, malabsorption, and urinary tract infection [1].
The urinary citric acid level cannot be used to estimate dietary intake because other factors, such as acid-base balance, may affect citrate excretion [2].
The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings.
References
1. Delaney, PM et al. Kidney disease. In: Rifai R, et al. eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier Inc; 2022.
2. Williams JC Jr, et al. Urolithiasis. 2021;49(1):1-16.
Citrate inhibits calcium stone formation by binding and solubilizing calcium, which reduces supersaturation of calcium salts [1-2]. Approximately half of the patients with calcium stones have decreased urinary citrate levels [1]. Citrate is among several substances routinely screened to evaluate the risk of forming kidney stones. Low urinary citrate levels may indicate oral citrate treatment in patients with recurrent calcium nephrolithiasis [1]. Other conditions that can cause hypocitraturia include distal renal tubular acidosis, malabsorption, and urinary tract infection [1].
The urinary citric acid level cannot be used to estimate dietary intake because other factors, such as acid-base balance, may affect citrate excretion [2].
The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings.
References
1. Delaney, PM et al. Kidney disease. In: Rifai R, et al. eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier Inc; 2022.
2. Williams JC Jr, et al. Urolithiasis. 2021;49(1):1-16.
Performing Laboratory
| Quest Diagnostics Nichols Institute-Chantilly VA |
| 14225 Newbrook Drive |
| Chantilly , VA 20151-2228 |
