Question 1

Why does MDRD systematically underestimate GFR >60?

Accepted Answer

The MDRD study population consisted exclusively of patients with CKD (mean measured GFR ~40). The equation was not designed for healthy populations and has a negative bias at higher GFR ranges. CKD-EPI was developed to address this limitation.

Question 2

Should I switch my lab from MDRD to CKD-EPI?

Accepted Answer

Yes, if possible. KDIGO recommends reporting eGFR using the CKD-EPI equation. The transition may affect the prevalence of CKD in the population (fewer false positives at GFR 60–75).

Question 3

Can MDRD be used for drug dosing?

Accepted Answer

It can be used, but CKD-EPI is now preferred. Drug labels may reference any of the three equations (Cockcroft-Gault, MDRD, CKD-EPI). Use the equation specified in the drug label or local formulary.

Question 4

How does MDRD handle the race variable?

Accepted Answer

The MDRD equation includes a multiplier (1.212) for Black patients. This race coefficient has been criticised for perpetuating race-based medicine. The 2021 CKD-EPI equation (without race) is the recommended alternative.