Update in Algorithm for Calculation of eGFR (10/10/12)

Dear Valued Partner:

Solstas Lab PartnersĀ®is pleased to announce that the algorithm that is being used for the calculation of eGFR (estimated Glomerular Filtration Rate) for the assessment of asymptomatic chronic kidney disease was updated to the newer CKD-EPI (Chronic Kidney Disease-Epidemiology Collaboration) equation, effective October 15, 2012.

Since 2005, Solstas Lab Partners has offered the eGFR as a calculation based on the serum creatinine value using the MDRD (Modification of Diet in Renal Disease) algorithm, which was historically recommended for use by the NKDEP (National Kidney Disease Education Program) (1). However, the CKD-EPI algorithm was recently developed and proposed as an alternative equation that reportedly estimated the measured GFR more accurately than the MDRD equation, particularly at higher values, which is where it would be most valuable as a screening tool (2).

Several studies have shown that the estimation of GFR by the CKD-EPI equation demonstrates improved clinical risk prediction than the MDRD equation, particularly at higher eGFR values (3,4,5). A meta-analysis of more than 1 million adults concluded that the CKD-EPI equation was more specific in the classification of chronic kidney disease and more accurately categorized the risk for mortality and ESRD (end-stage renal disease) than did the MDRD equation across a broad range of populations (4). A second meta-analysis of 12 studies from North America, Europe, and Australia concluded that the CKD-EPI equation performed better at higher eGFRs ( >60 mL/min per 1.73m2.(5) Based on these studies, the National Kidney Foundation has recently modified its recommendations to include the use of the CKD-EPI algorithm based on the greater accuracy of the CKD-EPI algorithm at these higher values (6), particularly for the screening of asymptomatic populations which tend to have results >60 mL/min and for labs who wish to report values between 60 and 90. Therefore, Solstas Lab Partners will now report eGFR values up to 90.

As before, these algorithms for estimating GFR are only validated for adults (18-70 years old) and for patients with stable creatinine concentrations, normal diets, and relatively normal muscle mass. The algorithm should not be used for children, hospitalized patients, pregnant women, or patients on vegetarian diets or with extremes in muscle mass (6).

CKD Stage
eGFR
Description

Stage 1
Stage 2
Stage 3
Stage 4
Stage 5
>90
60-89
30-59
15-29
<15
Normal GFR with other evidence of chronic kidney damage
Mild impairment with other evidence of chronic kidney damage
Moderate impairment
Severe impairment
End-Stage Kidney Disease (ESKD/ESRD) (or on dialysis)

If you have any questions, please call your dedicated Solstas Client Relationship Specialist directly, or contact our Client Services team at 1-888-664-7601. Thank you for choosing Solstas Lab Partners to serve the needs of you and your patients.

Janice J. Hessling, M.D., Ph.D
Corporate Medical Director

References
1.National Kidney Foundation. "Part 4. Definition and Classification of Stages of Chronic Kidney Disease" and Part 5. Evaluation of Laboratory Measurements for Clinical Assessment of Kidney Disease, Guideline 4. Estimation of GFR. Am J Kid Disease 2002, Suppl.1:S46
2.Levey AS, et al. 2009. A new equation to estimate glomerular filtration rate. Ann Intern Med. 150:604-612.
3. Michaels, WM et al. 2010. Performance of the Cockcroft-Gault, MDRD, and new CKD-EPI formulas in relation to GFR, age, and body size. Clin J Am Soc Nephrol. 5:1003-1009.
4. Matsushita, K., et al. 2012. Comparison of Risk Prediction using the CKD-EPI equation and the MDRD Study equation for estimated Glomerular Filtration Rate. JAMA 307:1941-1950.
5. Earley A, et al. 2012. Estimating equations for glomerular filtration rate in the era of creatinine standardization: a systematic review. Ann Intern Med. 156:785-95.
6. Estimating GFR. NKDEP.nih.gov/lab-evaluation/gfr/estimating.shtml. Updated June 6, 2012.