Which lab value is the most reliable indicator of kidney function?

• A. Estimated glomerular filtration rate (eGFR)
• B. Serum albumin
• C. Alkaline phosphatase
• D. Serum amylase

Answer: (A)

eGFR is the best single measure of kidney function because it estimates how much blood the kidneys are filtering each minute, taking into account creatinine levels along with age, sex, and sometimes race. This makes it a standardized gauge of filtration capacity across individuals and over time, which is why it’s used to stage kidney disease and monitor progression. Other values don’t reflect filtration rate: serum albumin changes with nutrition, liver disease, or kidney protein loss but doesn’t measure how well the kidneys filter; alkaline phosphatase points to bone or liver issues; and serum amylase indicates pancreatic activity. So, eGFR directly targets the kidneys’ filtering function, making it the most informative lab value for kidney function.