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Test ID: CREAZ    
Creatinine with Estimated GFR (MDRD), Serum

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Method Description Describes how the test is performed and provides a method-specific reference

Creatinine

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: Roche Cobas creatinine reagent, Roche Diagnostics, Indianapolis IN, August 2007)

 

Estimated Glomerular Filtration Rate (eGFR)

Serum creatinine is determined by an enzymatic colorimetric assay calibrated to an isotope dilution mass spectrometry (IDMS)-traceable method. The eGFR value is calculated from serum creatinine using the IDMS-traceable Modification of Diet in Renal Disease (MDRD) Study equation.(2) When creatinine is in mg/dL (conventional units) this equation is:

 

eGFR (mL/min/1.73 m[2]) =175 x Scr(-1.154) x Age(-0.203) x (0.742 if female) x (1.210 if African American)

 

The equation utilizes the following variables to calculated eGFR:

-Serum or plasma creatinine (Scr)

-Age in years (18 years or older)

-Sex

-Race (African American or non-African American

 

Exact values are reported for calculated GFR estimates <60 mL/min/1.73 m(2). Estimated GFR values >60 mL/min/1.73 m(2) are reported as ">60 mL/min/1.73 m(2)" and not as an exact number.

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 Sunday; Continuously

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.

Same day/1 day

Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result

2 days

Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

1 week

Performing Laboratory Location The location of the laboratory that performs the test

Rochester