Citric Acid, 24-Hour Urine with Creatinine

For Specimen Integrity during Extreme Weather see the “Lockbox Usage in Extreme Weather” document at the top of this page.

Test Code

CPT Codes
82507, 82570<br>** This test is not available for New York patient testing **

CPT code 81050 may be added at an additional charge for volume measurement

Preferred Specimen
10 mL of a 24-hour urine collected in a 24 hour urine container

Minimum Volume
1.5 mL

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 Temperature
Refrigerated (cold packs)

Specimen Stability
Room temperature: 8 hours
Refrigerated: 30 days
Frozen: 60 days

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Received room temperature • Acidified urine

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
Set up: Mon-Fri; Report available: 1 day

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.

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
14225 Newbrook Drive
Chantilly, VA 20153

Last Updated: December 7, 2021

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.