Difference between mGFR and eGFR-creatinine-cystatin C comparing the 2012 versus 2021 CKD-EPI creatinine-cystatin C equations

The equations are referred to by year of development. The vertical bars indicate 95% confidence intervals. The dotted black line represents the difference in the GFR equation performance between race groups.

(A) Bias as shown as median difference between mGFR and eGFR. Units are mL/min per 1.73 m². A positive number indicates underestimate of mGFR, and a negative number indicates overestimate of mGFR. Solid gray line is the line of identity. Dashed gray lines are drawn at the median difference of 5 and –5 mL/min per 1.73 m², which is defined as small bias.

(B) Accuracy as shown as percentage of eGFR values that differ from the corresponding mGFR by less than 30% (P₃₀). A P₃₀ of 90% is considered optimal; a P₃₀ between 80 to 90% is considered acceptable.

(C) Agreement between mGFR and eGFR categories using guideline-recommended CKD GFR (G) stages (<30, 30 to 44, 45 to 59, 60 to 89, and ≥90 mL/min per 1.73m²). More than 70% agreement is considered optimal, and between 60 to 70% is considered acceptable^[1-3].