Which factor most affects the accuracy of eGFR calculations?

Which factor most affects the accuracy of eGFR calculations?

• A. Sleep duration prior to testing.
• B. Meal content prior to drawing blood.
• C. Muscle mass and age.
• D. Time since last medication dose.

Answer: (C)

eGFR depends on serum creatinine, which is a byproduct of muscle metabolism. Since creatinine production is tied to how much muscle a person has, and because kidney function (and creatinine clearance) changes with age, muscle mass and age have the biggest impact on how accurate an eGFR calculation will be. More muscle means more creatinine, which can lower the estimated GFR even if kidney function is normal; less muscle or aging tends to reduce creatinine production and can inflate the eGFR. That's why this factor most strongly influences accuracy. Other factors can affect creatinine levels transiently or in specific situations, but they don't shift the estimate as consistently as the combination of muscle mass and age.

eGFR depends on serum creatinine, which is a byproduct of muscle metabolism. Since creatinine production is tied to how much muscle a person has, and because kidney function (and creatinine clearance) changes with age, muscle mass and age have the biggest impact on how accurate an eGFR calculation will be. More muscle means more creatinine, which can lower the estimated GFR even if kidney function is normal; less muscle or aging tends to reduce creatinine production and can inflate the eGFR. That's why this factor most strongly influences accuracy.

Other factors can affect creatinine levels transiently or in specific situations, but they don't shift the estimate as consistently as the combination of muscle mass and age.