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POCT Creatinine with eGFR
|Performed by||Authorized Point of Care testing site staff|
|Method||Enzymatic amperometric (iStat)
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|Container type||Fingerstick sample or Light green top|
|Amount to Collect||
|Sample type||Capillary blood or Heparinized whole blood|
|Min. Volume||1 drop blood|
Note: The eGFR is calculated by nursing staff using an on-line calculator:
Click here for calculator
|Normal range|| Creatinine
|Stability||Room temperature 30 minutes|
|Additional information||To convert mg/dL to µmol/L (SI units) multiply by 88.4. See method details for assay limitations and drug interferences.
Measurements of whole blood creatinine with this point of care assay are are approximately 0.2 mg/dL higher than measurements of plasma creatinine with the Beckman Synchron assay used in the central laboratory. Although the manufacturer of the point of care assay claims standardization traceable to the isotope dilution mass spectrometry (IDMS) reference method, this point of care assay shows a systematic positive bias versus the IDMS traceable method used in the central laboratory (similar to the systematic bias observed with non-IDMS traceable creatinine assays). To minimize the impact of this positive bias on eGFR measurements, calculations of eGFR using the whole blood point of care creatinine results are performed using the MDRD study equation for non-IDMS traceable creatinine methods.
GFR (mL/min/1.73 m2) = 186 x (Scr)-1.154 x (Age)-0.203 x (0.742 if female) x (1.210 if African-American)
The normal range for serum creatinine in adults was verified using donor samples collected from our Donor Center (excludes autologous donors). We adopted the manufacturer's adult reference range of 0.6 to 1.3 mg/dL.
Because the MDRD formula is not considered sufficiently accurate for estimating GFR in patients with normal or mildly reduced renal function, results greater than 60 mL/min/1.73 meters squared body surface area are displayed as > 60 mL/min and are not reported as an exact number. Note that the estimated GFR result is not reliable in certain groups including severely ill patients. The MDRD equation used to estimate GFR has been validated only in Caucasian and African Americans 18 – 70 years of age. The equation has not been validated in other population groups, pregnant women, transplant recipients, medically unstable patients including those with acute renal failure, or in persons with extremes of body size, muscle mass, or nutritional status. Application of the MDRD calculation in these cases may lead to errors in GFR estimation. Click here for more information on this topic
GFR can also be estimated from serum creatinine in adults by the older formula of Cockcroft DW, Gault MH: (Nephron 1976;16:31) :
For women, multiply the calculated result by 0.85
Note that the Cockcroft-Gault formula is susceptible to many of the same limitations of the MDRD formula and may overestimate GFR by 16% or more when using current methods of creatinine measurement.
According to the National Kidney Disease Education Program, the best equation for estimating glomerular filtration rate (GFR) from serum creatinine in children is the Bedside Isotope Dilution Mass Spectrometry (IDMS)-traceable Schwartz equation
Click here for on line calculator based on Schwartz Formula
Bedside IDMS-traceable Schwartz Equation for Children
GFR (mL/min/1.73 m2) = (0.41 x Height in cm) / Creatinine in mg/dL)
|Last Updated||10/4/2013 9:52:49 PM|