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Test Code CRT2F Creatinine, 24 Hour, Urine


Specimen Required


Only orderable as part of a profile. For more information see:

-TLTE4 / Leukotriene E4, 24 Hour, Urine

-MCM24 / Mast Cell Mediators, 24 Hour, Urine


Useful For

Normalizing urinary analytes to account for the variation in urinary concentration

Method Name

Only orderable as part of a profile. For more information see:

-TLTE4 / Leukotriene E4, 24 Hour, Urine

-MCM24 / Mast Cell Mediators, 24 Hour, Urine

 

Enzymatic Colorimetric Assay

Reporting Name

Creatinine, 24 HR, U

Specimen Type

Urine

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Frozen (preferred) 30 days
  Refrigerated  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 filtered creatinine is excreted in the urine. Renal tubular secretion of creatinine contributes a small proportion of excreted creatinine. Although most excreted creatinine is derived from an individual's muscle mass, 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:

-TLTE4 / Leukotriene E4, 24 Hour, Urine

-MCM24 / Mast Cell Mediators, 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 younger than 18 years.

Interpretation

Decreased creatinine clearance indicates decreased glomerular filtration rate. This can be due to conditions, such as progressive kidney 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 frequently seen during pregnancy or in patients with diabetes mellitus before diabetic nephropathy has occurred. It may also 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. According to Clinical and Laboratory Standards Institute guidelines, methyldopa, as tested, causes artificially low creatinine results.

 

Dicynene (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.

Day(s) Performed

Monday through Sunday

Report Available

1 day

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
CRT2F Creatinine, 24 HR, U 65634-8

 

Result ID Test Result Name Result LOINC Value
CR_AF Creatinine, 24 HR, U 2162-6
TM10F Collection Duration (h) 13362-9
VL8F Urine Volume (mL) 3167-4
CRF24 Creatinine Concentration, 24 HR, U 20624-3