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LABORATORY MEDICINE UPDATE

August 23, 2013

Changes in Reporting of Estimated Glomerular Filtration Rate (eGFR)

In keeping with new recommendations1, the laboratory will report estimated GFR by use of the CKD-EPI equation2 rather than the older MDRD equation.3,4

The newer equation allows reporting of numerical eGFR results above 60 ml/min/1.73 m2 and encompasses a wider age-range of patients (ages 18 to 85 years).

Coincident with this change:

·  The laboratory will report a separate eGFR result for black and nonblack patients with each creatinine. The comment to multiply by 1.2 if black will no longer appear.

·  CKD Stage 3 will be reported as Stages 3a (45-59 ml/min/1.73 m2) and Stage 3b (30-44 ml/min/1.73 m2).1

As a reminder, the eGFR is not reliable in some people:

·  Individuals with unstable creatinine concentrations.This includes pregnant women; patients with serious co-morbid conditions; and hospitalized patients, particularly those with acute renal failure. When renal function changes, the serum creatinine requires time to reach a new steady state that reflects GFR.

·  Persons with extremes in muscle mass and diet.This includes: amputees, paraplegics, bodybuilders, and obese subjects; patients who have a muscle-wasting disease or a neuromuscular disorder; and those suffering from malnutrition, eating a vegetarian or low-meat diet, or taking creatine dietary supplements.

·  Individuals under the age of 18. The recently published equation for children with chronic kidney disease5 requires additional information.

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1. Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2012 Clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney International Suppl 2013;3:1-150.

2. Levey AS, Stevens LA, Schmid CH; Zhang YL, Castro III AF, Feldman HI et al. for the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration). A new equation to estimate glomerular filtration rate. Ann Intern Med 2009;150:604-12.

3. Modification of Diet in Renal Disease Study Group. A more accurate method to estimate glomerular filtration rate from serum creatinine: a new prediction equation. Ann Intern Med 1999;130:461-70.

4. Levey AS, Coresh J, Greene T, Marsh J, Stevens LS, Kusek J et al. for Chronic Kidney Disease Epidemiology Collaboration. Expressing the modification of diet in renal disease study equation for estimating glomerular filtration rate with standardized serum creatinine values. Clin Chem 2007;53:766-72.

5. Schwartz GJ, Schneider MF. Maier PS, Moxey-Mims M, Dharnidharka VR, Warady BA et al. Improved equations estimating GFR in children with chronic kidney disease using an immunonephelometric determination of cystatin C. Kidney International 2012;82:445-53.

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