Which factors influence the accuracy of eGFR estimates?

• A. Age, sex, race, body size, muscle mass, diet, and rapidly changing renal function.
• B. Eye color and hair color.
• C. Blood type.
• D. Seasonal variation in creatinine.

Answer: (A)

eGFR accuracy hinges on factors that influence creatinine production and the stability of its concentration in the blood. Since eGFR is calculated from serum creatinine, anything that changes how much creatinine the body makes or how quickly it is cleared will affect the estimate.

Age, sex, race, body size, and muscle mass shape baseline creatinine production because muscle is the main source of creatinine. Individuals with more muscle mass or certain demographic characteristics generally produce more creatinine, which shifts the calculated eGFR if the same serum level is used. Diet matters too; recent high meat intake or high-protein diets can raise serum creatinine temporarily, altering the estimate. If kidney function is changing rapidly, the serum creatinine may not yet reflect the new GFR, so the eGFR can lag behind true changes in kidney function and become inaccurate.

Choices like eye color, hair color, or blood type do not affect creatinine generation or the eGFR calculation. Seasonal variation in creatinine is not a routine determinant of eGFR accuracy.