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Test ID CACR3 Calcium/Creatinine Ratio, Random, Urine


Specimen Required


Supplies: Aliquot Tube, 5 mL (T465)

Collection Container/Tube: Clean, plastic urine container with no metal cap or glued insert

Submission Container/Tube: Plastic, 5-mL tube or a clean, plastic aliquot container with no metal cap or glued insert

Specimen Volume: 4 mL

Collection Instructions:

1. Collect a random urine specimen.

2. No preservative.


Useful For

Evaluation of calcium oxalate and calcium phosphate kidney stone risk

 

Calculation of urinary supersaturation

 

Evaluation of bone diseases, including osteoporosis and osteomalacia

Profile Information

Test ID Reporting Name Available Separately Always Performed
CCTR Calcium/Creat Ratio, Random, U No Yes
CALC5 Calcium, Random, U No Yes
CRETR Creatinine, Random, U No Yes

Method Name

CALC5: Photometric

CRETR: Enzymatic Colorimetric Assay

Reporting Name

Calcium/Creat Ratio, Random, U

Specimen Type

Urine

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Refrigerated (preferred) 14 days
  Frozen  30 days
  Ambient  72 hours

Clinical Information

Calcium is the fifth most common element in the body. It is a fundamental element necessary to form electrical gradients across membranes, an essential cofactor for many enzymes, and the main constituent in bone. Under normal physiologic conditions, the concentration of calcium in serum and in cells is tightly controlled. Calcium is excreted in both urine and feces. Ordinarily about 20% to 25% of dietary calcium is absorbed, and 98% of filtered calcium is reabsorbed in the kidney. Traffic of calcium between the gastrointestinal tract, bone, and kidney is tightly controlled by a complex regulatory system that includes vitamin D and parathyroid hormone. Sufficient bioavailable calcium is essential for bone health. Excessive excretion of calcium in the urine is a common contributor to kidney stone risk.

Reference Values

1 month-<12 months: 0.03-0.81 mg/mg creat

12 months-<24 months: 0.03-0.56 mg/mg creat

24 months-<3 years: 0.02-0.50 mg/mg creat

3 years-<5 years: 0.02-0.41 mg/mg creat

5 years-<7 years: 0.01-0.30 mg/mg creat

7 years-<10 years: 0.01-0.25 mg/mg creat

10 years-<18 years: 0.01-0.24 mg/mg creat

18 years-83 years: 0.05-0.27 mg/mg creat

Reference values have not been established for patients who are less than 1 month of age.

Reference values have not been established for patients who are greater than 83 years of age.

Interpretation

Increased urinary calcium excretion (hypercalciuria) is a known contributor to kidney stone disease and osteoporosis.

 

Many cases are genetic (often termed "idiopathic"). Previously such patients were often divided into fasting versus absorptive hypercalciuria depending on the level of urine calcium in a fasting versus fed state, but the clinical utility of this approach is now in question. Overall, the risk of stone disease appears increased when 24-hour urine calcium is greater than 250 mg in men and greater than 200 mg in women. Thiazide diuretics are often used to reduce urinary calcium excretion, and repeat urine collections can be performed to monitor the effectiveness of therapy.

 

Known secondary causes of hypercalciuria include hyperparathyroidism, Paget disease, prolonged immobilization, vitamin D intoxication, and diseases that destroy bone (such as metastatic cancer or multiple myeloma).

 

Urine calcium excretion can be used to gauge the adequacy of calcium and vitamin D supplementation, for example in states of gastrointestinal fat malabsorption that are associated with decreased bone mineralization (osteomalacia).

Clinical Reference

1. Fraser WD: Bone and mineral metabolism. In: Rifai N, Horwath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018:1438

2. Curhan GC, Willett WC, Speizer FE, Stampfer MJ: Twenty-four-hour urine chemistries and the risk of kidney stones among women and men. Kidney Int. 2001;59:2290-2298

3. Metz MP: Determining urinary calcium/creatinine cut-offs for the pediatric population using published data. Ann Clin Biochem. 2006;43:398-401

4. Pak CY, Britton F, Peterson R, et al: Ambulatory evaluation of nephrolithiasis. Classification, clinical presentation and diagnostic criteria. AM J Med. 1980;69:19-30

5. Pak CY, Kaplan R, Bone H, et al: A simple test for the diagnosis of absorptive, resorptive and renal hypercalciurias. N Engl J Med. 1975;292:497-500

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

82310

82570

LOINC Code Information

Test ID Test Order Name Order LOINC Value
CACR3 Calcium/Creat Ratio, Random, U 9321-1

 

Result ID Test Result Name Result LOINC Value
CCTR Calcium/Creat Ratio, Random, U 9321-1
CALC5 Calcium, Random, U 17862-4
CRETR Creatinine, Random, U 2161-8

Day(s) Performed

Monday through Sunday

Report Available

1 to 3 days