Which biomarker is commonly used as an index of overall renal function?

• A. Creatinine
• B. Urea
• C. Uric acid
• D. Glucose

Answer: (A)

Creatinine is produced at a relatively constant rate from muscle metabolism and is freely filtered by the kidneys with essentially no reabsorption. Because of this, the amount of creatinine cleared from the blood by the kidneys closely reflects the glomerular filtration rate (GFR). In clinical practice, serum creatinine is used to estimate GFR (eGFR), providing a convenient index of overall renal function.

Urea (BUN) can vary a lot with hydration status, protein intake, liver function, and catabolic states, so it’s a less specific measure of filtration. Uric acid levels are influenced by purine metabolism and tubular handling and are not used as a general index of kidney function. Glucose reflects energy metabolism and diabetic control, not renal filtration capacity, so it doesn’t serve as a renal function marker.

Thus, creatinine stands out as the best single biomarker for assessing overall renal function because its production is relatively stable and its clearance by the kidneys directly mirrors filtration ability, forming the basis for widely used eGFR calculations.