Calcium/Creatinine Ratio, Random, Urine
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Identification of abnormal physiologic states causing excess or suppressed excretion of calcium, such as hyperparathyroidism, vitamin D abnormality, diseases that destroy bone, prostate cancer, and drug treatment, such as thiazide therapy.
Profile Information A profile is a group of laboratory tests that are ordered and performed together under a single Mayo Test ID. Profile information lists the test performed, inclusive of the test fee, when a profile is ordered and includes reporting names and individual availability.
|Test ID||Reporting Name||Available Separately||Always Performed|
|CALRR||Calcium, Random, U||Yes, (order CAUR)||Yes|
|CTURR||Creatinine, Random, U||No||Yes|
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
CALRR: Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES)
CTURR: Enzymatic Colorimetric Assay
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Calcium/Creat, Random, U
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Collection Container/Tube: Clean, plastic urine collection container
Submission Container/Tube: Plastic, 6-mL tube (Supply T465) or a clean, plastic aliquot container with no metal cap or glued insert
Specimen Volume: 3 mL
1. Collect a random urine specimen.
2. See Metals Analysis-Collection and Transport in Special Instructions for complete instructions.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
|Urine||Refrigerated (preferred)||28 days|
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
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 exists in 3 states in the body; bound to protein, bound to small anions, and in the free (ionized) state. The concentration of serum calcium in the ionized state is regulated by parathyroid hormone (PTH) and 1,25 dihydroxy vitamin D.
Circulating calcium is excreted by glomerular filtration and reabsorbed in the proximal tubules. Calcium reabsorption in the proximal tubule is affected by tubular sodium concentration, whereas PTH induces calcium uptake in the distal tubule and the collecting duct. Excess is excreted in the urine and the feces.
Because PTH increases renal tubular reabsorption of calcium, one would expect patients with hyperparathyroidism to be hypocalciuric. However, highly urinary calcium/creatinine ratios were found in most hyperparathyroid patients, and less frequently in patients with hypercalcemia due to other causes.
Calcium/creatinine ratio of random urine specimens may be used to detect hypercalciuria in patients suspected of having metabolic bone disease or other abnormalities of calcium metabolism.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
0-12 months: <2,100 mg/g
13-24 months: <450 mg/g
25 months-5 years: <350 mg/g
6-10 years: <300 mg/g
11-18 years: <260 mg/g
> or =19 years: <220 mg/g
Increased urinary excretion of calcium accompanies hyperparathyroidism, vitamin D intoxication, diseases that destroy bone (such as multiple myeloma), metastasis from prostatic cancer, and following calcium supplementation.
Patients with absorptive hypercalciuria (increased gut absorption) will have lowered urine calcium with dietary restriction and, therefore, can be differentiated from patients with hypercalciuria caused by hyperparathyroidism, hyperthyroidism, Paget's disease, or "renal leak" type of calciuria as seen in renal tubular acidosis.
Thiazide drugs tend to reduce excretion of calcium.
For individuals consuming an average daily intake of 600 mg to 800 mg of calcium per day, the normal daily excretion of calcium is:
-Males: 25 mg to 300 mg
-Females: 20 mg to 275 mg
The normal urine calcium/creatinine ratio is <220 mg/g.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
No significant cautionary statements
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Metz JP: Determining urinary calcium/creatinine cutoffs for the pediatric population using published data. Ann Clin Biochem 2006 Sep;43(Pt 5):398-401
2. Saleh F, Jorde R, Sartberg J, et al: The relationship between blood pressure and serum parathyroid hormone with special reference to urinary calcium excretion: the Tromso Study. J Endocrinol Invest 2006 Mar;29(3):214-220
3. Christensen SE, Nissen PH, Vestergaard P, et al: Discriminative power of three indices of renal calcium excretion for the distinction between familial hypocalcuric hypercalemia and primary hyperparathyroidism: a follow-up study on methods. Clin Endocrinol 2008 Nov;69(5):713-720
Method Description Describes how the test is performed and provides a method-specific reference
Calcium concentration is determined by inductively coupled plasma optical emission spectrometry. Aqueous acidic calibrating standards, quality control samples, patient specimens, and blanks are diluted with diluent containing an internal standard. In turn, all diluted blanks, calibrating standards, quality control samples, and patient samples are aspirated into a pneumatic nebulizer and the resulting aerosol directed to the hot plasma discharge by a flow of argon. In the annular plasma the aerosol is vaporized, atomized, and then ionized. Emission signals from calcium and the internal standard are observed radially by the emission spectrometer. Instrumentation response is defined by the linear relationship of analyte concentrations versus the ratio of the calcium emission signals ratioed with the internal standard. After reagent blank subtraction, unknown sample calcium concentrations are calculated by entering the net unknown intensity ratios into the linear calibration equation.(Nixon DE, Moyer TP, Johnson P, et al: Routine measurement of calcium, magnesium, copper, zinc, and iron in urine and serum by inductively coupled plasma emission spectroscopy. Clin Chem 1986;32:1660-1665)
Creatinine is measured using an enzymatic method based on the determination of sarcosine from creatinine with the aid of creatininase, creatinase, and sarcosine oxidase. The liberated hydrogen peroxide is measured via a modified Trinder reaction using a colorimetric indicator.(Package insert: Roche Diagnostics, Indianapolis IN, 2004)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday; 11 a.m.-6 p.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
|Result ID||Reporting Name||LOINC Code|
|31171||Calcium, Random, U||17862-4|
|RCTUR||Creatinine, Random, U||2161-8|