Specialized Testing

GFR (Glomerular Filtration Rate)

Regional Medical Laboratory - Reference range for GFR African American and non-African American

Normal GFR: >60 mL/Min.
Moderately decreased GFR: 30-59 mL/Min.
Severely decreased GFR: 15-29 mL/Min.
Kidney failure (or Dialysis): <15 mL/Min.

MDRD equation for calculated GFR has not been validated for use with the elderly (over 70 years of age.) GFR estimating equations have poorer agreement with measured GFR for ill hospitalized patients. GFR was calculated utilizing an IDMS traceable creatinine result. (02/03/08)

The National Kidney Disease Education Program (NKDEP) of the National Institute of Diabetes and Diseases of the Kidney (NIDDK), National Kidney Foundation (NKF) and American Society of Nephrology (ASN) recommend estimating GFR from serum creatinine using the MDRD Study equation. This equation uses serum creatinine in combination with age, sex and race to estimate GFR and therefore improves upon several of the limitations with the use of serum creatinine. The MDRD Study equation has been rigorously developed and validated, is more accurate than measured creatinine clearance from 24-hour urine collections, because although creatinine clearance approximates GFR it overestimates it due to the fact that creatinine is secreted in the proximal tubule. Measurement of creatinine clearance requires collection of a timed urine sample, which is inconvenient and frequently inaccurate.

Online Calculator

For more information of the GFR, the National Kidney Disease Education Program provides excellent information, including a GFR calculator for you PDA.

For available online GFR calculators visit: http://nkdep.nih.gov/lab-evaluation/gfr-calculators.shtml