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HelpTest Code CRT24 Creatinine, 24 Hour, Urine
Specimen Required
Only orderable as part of a profile. For more information see:
-NMH24 / N-Methylhistamine, 24 Hour, Urine
-RB24 / Retinol-Binding Protein, 24 Hour, Urine
-A124 / Alpha-1-Microglobulin, 24 Hour, Urine
Useful For
Urinary creatinine, in conjunction with serum creatinine, is used to calculate the creatinine clearance, a measure of renal function
Normalizing urinary analytes to account for the variation in urinary concentration
Method Name
Only orderable as part of a profile. For more information see:
-NMH24 / N-Methylhistamine, 24 Hour, Urine
-RB24 / Retinol-Binding Protein, 24 Hour, Urine
-A124 / Alpha-1-Microglobulin, 24 Hour, Urine
Enzymatic Colorimetric Assay
Reporting Name
Creatinine, 24 HR, USpecimen Type
UrineSpecimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Refrigerated (preferred) | 30 days | |
| Frozen | 30 days | ||
| Ambient | 14 days |
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Clinical Information
Creatinine is formed from the metabolism of creatine and phosphocreatine, both of which are principally found in muscle. Thus, the amount of creatinine produced is in large part dependent upon the individual's muscle mass and tends not to fluctuate much from day-to-day.
Creatinine is not protein-bound and is freely filtered by glomeruli. All of the filtered creatinine is excreted in the urine.
Renal tubular secretion of creatinine also contributes to a small proportion of excreted creatinine. Although most excreted creatinine is derived from an individual's muscle, dietary protein intake, particularly of cooked meat, can contribute to urinary creatinine levels.
The renal clearance of creatinine provides an estimate of glomerular filtration rate.
Reference Values
Only orderable as part of a profile. For more information see:
-NMH24 / N-Methylhistamine, 24 Hour, Urine
-RB24 / Retinol-Binding Protein, 24 Hour, Urine
-A124 / Alpha-1-Microglobulin, 24 Hour, Urine
Normal values mg per 24 hours:
Males: 930-2955 mg/24 hours
Females: 603-1783 mg/24 hours
Reference values have not been established for patients who are less than 18 years of age.
For SI unit Reference Values, see https://www.mayocliniclabs.com/order-tests/si-unit-conversion.html
Interpretation
Decreased creatinine clearance indicates decreased glomerular filtration rate. This can be due to conditions such as progressive renal disease, or result from adverse effect on renal hemodynamics that are often reversible including certain drugs or from decreases in effective renal perfusion (eg, volume depletion or heart failure).
Increased creatinine clearance is often referred to as "hyperfiltration" and is most commonly seen during pregnancy or in patients with diabetes mellitus, before diabetic nephropathy has occurred. It also may occur with large dietary protein intake.
Cautions
The reliability of 24-hour urinary creatinine determinations is, as for all timed urine collections, very dependent on accurately collected 24-hour specimens.
Intraindividual variability in creatinine excretion may be due to differences in muscle mass or amount of ingested meat.
Acute changes in glomerular filtration rate, before a steady state has developed, will alter the amount of urinary creatinine excreted.
Rifampicin, levodopa, and calcium dobesilate (eg, Dexium) cause artificially low creatinine results. As tested, according to CLSI recommendation, methyldopa causes artificially low creatinine results.
Dicynone (Etamsylate) at therapeutic concentrations may lead to falsely low results.
N-ethylglycine at therapeutic concentrations and DL-proline at concentrations greater or equal to 1 mmol/L gives falsely high results.
Method Description
The enzymatic method is 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. Optimization of the buffer system and the colorimetric indicator enables the creatinine concentration to be quantified both precisely and specifically.(Package insert: Creatinine plus ver 2. Roche Diagnostics; V 15.0 03/2019)
Performing Laboratory
Mayo Clinic Laboratories in Rochester
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.LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| CRT24 | Creatinine, 24 HR, U | 65634-8 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| CR_A | Creatinine, 24 HR, U | 2162-6 |
| TM27 | Collection Duration (h) | 13362-9 |
| VL69 | Urine Volume (mL) | 3167-4 |
| CR_24 | Creatinine Concentration, 24 HR, U | 20624-3 |
Day(s) Performed
Monday through Sunday