Which measurement is used to estimate GFR in adults?

• A. Serum creatinine with eGFR calculation (CKD-EPI or MDRD)
• B. Urine protein alone
• C. Serum albumin
• D. Blood urea nitrogen alone

Answer: (A)

Estimating GFR in adults is done most commonly using serum creatinine levels entered into an eGFR equation, such as CKD-EPI or MDRD. Creatinine is a waste product produced at a relatively steady rate by muscle and is filtered by the kidneys; the amount in the blood reflects how well the kidneys are filtering. The eGFR equations adjust for factors like age, sex, and race to improve accuracy across adult patients. This combination makes serum creatinine with an eGFR calculation the standard way to estimate GFR. Urine protein indicates kidney damage but not filtration rate, serum albumin reflects nutritional or liver status, and blood urea nitrogen can be affected by hydration and protein intake and does not reliably estimate GFR on its own.