NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Estimation of glomerular filtration rate
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|
|CREAS||Creatinine, S||Yes, (order CREAZ)||Yes|
Enzymatic Colorimetric Assay
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Creatinine Clearance, Serum & Urine
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.
Serum and urine are required. Serum must be drawn within the same 24-hour period as the urine collection.
Specimen Type: Serum
Container/Tube: Red top or serum gel
Specimen Volume: 1 mL
Collection Instructions: Label specimen as serum.
Specimen Type: Urine
Container/Tube: Plastic, 6-mL tube (Supply T465)
Specimen Volume: 5 mL
1. Collect urine for 24 hours.
2. No preservative.
3. Label specimen as urine.
1. 24-Hour volume and patient's height in centimeters and weight in kilograms are required.
2. See Urine Preservatives in Special Instructions for multiple collections.
Urine Preservative Collection Options
50% Acetic Acid
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.
Serum: 0.5 mL; Urine 1 mL
Mild OK; Gross reject
Mild reject; Gross reject
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Glomerular filtration rate (GFR) is the sum of filtration rates in all functioning nephrons and so an estimation of the GFR provides a measure of functioning nephrons of the kidney. A decrease in GFR implies either progressive renal disease, or a reversible process causing decreased nephron function (eg, severe dehydration). One of the most common methods used for estimating GFR is creatinine clearance.
Creatinine is derived from the metabolism of creatine from skeletal muscle and dietary meat intake, and is released into the circulation at a relatively constant rate. Thus, the serum creatinine concentration is usually stable. Creatinine is freely filtered by glomeruli and not reabsorbed or metabolized by renal tubules. However, approximately 15% of excreted urine creatinine is derived from proximal tubular secretion. Because of the tubular secretion of creatinine, the creatinine clearance typically overestimates the true GFR by 10% to 15%.
Creatinine clearance is usually determined from measurement of creatinine in a 24-hour urine specimen and from a serum specimen obtained during the same collection period. The creatinine clearance is then calculated by the equation:
2.54 cm=1 inch
1 kg=2.2 pounds (lbs)
Patient surface area (SA)=wt (kg)(.425) X ht (cm)(.725) X 0.007184
Urine conc (mg/dL) x 24 hr Urine volume (mL)
Uncorr creat clear= 1440 minutes_____ =mL/min
Plasma creat (mg/dL)
Urine conc (mg/dL) x 24 hr urine volume (mL)
Corr creat clear= 1440 minutes_______ x 1.73m(2)=
Plasma creat (mg/dL) Patient SA
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.
0-18 years: Reference values have not been established
19-75 years: 77-160 mL/min/BSA
> or =76 years: Reference values have not been established
0-17 years: Reference values have not been established
18-29 years: 78-161 mL/min/BSA
30-39 years: 72-154 mL/min/BSA
40-49 years: 67-146 mL/min/BSA
50-59 years: 62-139 mL/min/BSA
60-72 years: 56-131 mL/min/BSA
> or =73 years: Reference values have not been established
Creatinine, Urine: reported in units of mg/dL
12-24 months: 0.1-0.4 mg/dL
3-4 years: 0.1-0.5 mg/dL
5-9 years: 0.2-0.6 mg/dL
10-11 years: 0.3-0.7 mg/dL
12-13 years: 0.4-0.8 mg/dL
14-15 years: 0.5-0.9 mg/dL
> or =16 years: 0.8-1.3 mg/dL
Reference values have not been established for patients that are less than 12 months of age.
13-36 months: 0.1-0.4 mg/dL
4-5 years: 0.2-0.5 mg/dL
6-8 years: 0.3-0.6 mg/dL
9-15 years: 0.4-0.7 mg/dL
> or =16 years: 0.6-1.1 mg/dL
Reference values have not been established for patients that are less than 12 months of age.
Decreased creatinine clearance indicates decreased glomerular filtration rate (GFR). This can be due to conditions such as progressive renal disease, or result from adverse effect on renal hemodynamics that are often reversible, including drug effects or decreases in effective renal perfusion (eg, volume depletion, 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 may also occur with large dietary protein intake.
A major limitation of creatinine clearance is that its accuracy worsens in relation to the amount of tubular creatinine secretion. Often as GFR declines, the contribution of urine creatinine from tubular secretion increases, further increasing the discrepancy between true GFR and measured creatinine clearance.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
One of the major limitations of creatinine clearance is erroneous results due to incomplete urine collections. Accurate results depend upon a complete and accurately timed collection.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Post TW, Rose BD: Assessment of renal function: plasma creatinine; BUN; and GFR. In UpTo Date 9.1. Edited by BD Rose. 2001
2. Kasiske BL, Keane WF: Laboratory assessment of renal disease: clearance, urinalysis, and renal biopsy. In The Kidney. Sixth edition. Edited by BM Brenner. Philadelphia, WB Saunders Company, 2000, pp 1129-1170
Method Description Describes how the test is performed and provides a method-specific reference
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 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 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.
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
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions.
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|