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HelpTest Code CITR Citrate Excretion, 24 Hour, Urine
Necessary Information
Patient's age and 24-hour volume (in milliliters) are required.
Specimen Required
Patient Preparation: Any drug that causes alkalemia or acidemia may be expected to alter citrate excretion and should be avoided, if possible. The patient must avoid laxative use for 24 hour collection period.
Supplies:
-Diazolidinyl Urea (Germall) 5.0 mL (T822)
-Sarstedt 5 mL Aliquot Tube (T914)
Container/Tube: Plastic tube
Specimen Volume: 4 mL
Collection Instructions:
1. Add 5 mL of diazolidinyl urea (Germall) as preservative at start of collection or refrigerate specimen during and after collection.
2. Collect urine for 24 hours.
3. Mix well before taking 4-mL aliquot.
Additional Information: See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens for multiple collections.
Forms
If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.
Useful For
Diagnosing risk factors for patients with calcium kidney stones
Monitoring results of therapy in patients with calcium stones or renal tubular acidosis
Special Instructions
Method Name
Enzymatic
Reporting Name
Citrate Excretion, 24 Hr, USpecimen Type
UrineSpecimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Refrigerated (preferred) | 14 days | |
| Frozen | 14 days |
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Clinical Information
Urinary citrate is a major inhibitor of kidney stone formation due in part to binding of calcium in urine. Low urine citrate levels are considered a risk for kidney stone formation.
Several metabolic disorders are associated with low urine citrate. Any condition that lowers renal tubular pH or intracellular pH may decrease citrate (eg, metabolic acidosis, increased acid ingestion, hypokalemia, or hypomagnesemia).
Low urinary citrate promotes kidney stone formation and growth, and is subject to therapy by correcting acidosis, hypokalemia, or hypomagnesemia by altering diet or using drugs such as citrate and potassium.
Reference Values
0-19 years: not established
20 years: 150-1,191 mg/24 hours
21 years: 157-1,191 mg/24 hours
22 years: 164-1,191 mg/24 hours
23 years: 171-1,191 mg/24 hours
24 years: 178-1,191 mg/24 hours
25 years: 186-1,191 mg/24 hours
26 years: 193-1,191 mg/24 hours
27 years: 200-1,191 mg/24 hours
28 years: 207-1,191 mg/24 hours
29 years: 214-1,191 mg/24 hours
30 years: 221-1,191 mg/24 hours
31 years: 228-1,191 mg/24 hours
32 years: 235-1,191 mg/24 hours
33 years: 242-1,191 mg/24 hours
34 years: 250-1,191 mg/24 hours
35 years: 257-1,191 mg/24 hours
36 years: 264-1,191 mg/24 hours
37 years: 271-1,191 mg/24 hours
38 years: 278-1,191 mg/24 hours
39 years: 285-1,191 mg/24 hours
40 years: 292-1,191 mg/24 hours
41 years: 299-1,191 mg/24 hours
42 years: 306-1,191 mg/24 hours
43 years: 314-1,191 mg/24 hours
44 years: 321-1,191 mg/24 hours
45 years: 328-1,191 mg/24 hours
46 years: 335-1,191 mg/24 hours
47 years: 342-1,191 mg/24 hours
48 years: 349-1,191 mg/24 hours
49 years: 356-1,191 mg/24 hours
50 years: 363-1,191 mg/24 hours
51 years: 370-1,191 mg/24 hours
52 years: 378-1,191 mg/24 hours
53 years: 385-1,191 mg/24 hours
54 years: 392-1,191 mg/24 hours
55 years: 399-1,191 mg/24 hours
56 years: 406-1,191 mg/24 hours
57 years: 413-1,191 mg/24 hours
58 years: 420-1,191 mg/24 hours
59 years: 427-1,191 mg/24 hours
60 years: 434-1,191 mg/24 hours
>60 years: not established
Interpretation
Any value less than the mean for 24 hours represents a potential risk for kidney stone formation and growth. Patients with low urinary citrate and new or growing stone formation, may benefit from adjustments in therapy known to increase urinary citrate excretion. (See Clinical Information)
Very low levels (<150 mg/24 hours) suggest investigation is needed for the possible diagnosis of metabolic acidosis (eg, renal tubular acidosis).
Cautions
Drugs that lower systemic pH, potassium, and/or magnesium also lower urine citrate and are to be avoided in patients with a tendency to form calcium stones.
Conversely, drugs that raise systemic pH, potassium, and/or magnesium, may raise urine citrate and should be considered when treating patients or interpreting results.
Method Description
Citric acid in the presence of zinc (2+) at pH 8.2 is catalyzed to oxaloacetate by the enzyme, citrate lyase. Oxaloacetate in the presence of malate dehydrogenase and reduced nicotinamide adenine dinucleotide (NADH) is reduced to malate (II). The citric acid concentration in the reaction mixture can be determined by measuring the disappearance of the light-absorbing NADH. By correcting this concentration for dilution and 24-hour volume, the amount of citric acid excreted per 24 hours is obtained.(Nielsen TT: A method for enzymatic determination of citrate in serum and urine. Scand J Clin Lab Invest 1976;36:513-519; Delaney MP, Lamb EJ: Kidney disease. In: Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018:1309-1310)
Day(s) Performed
Monday through Saturday
Report Available
Same day/1 daySpecimen Retention Time
7 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
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
82507
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LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| CITR | Citrate Excretion, 24 Hr, U | 6687-8 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| CITRT | Citrate Excretion, 24 Hr, U | 6687-8 |
| TM51 | Collection Duration | 13362-9 |
| VL49 | Urine Volume | 3167-4 |