Symmetric dimethylarginine (SDMA) is used to monitor decline in which renal metric?

• A. Blood urea nitrogen
• B. Creatinine clearance
• C. Glomerular filtration rate (GFR)
• D. Urine specific gravity

Answer: (C)

SDMA tracks kidney filtration function. It is produced at a steady rate and is cleared almost exclusively by glomerular filtration, so as GFR falls, SDMA rises. Because its production is relatively constant and it’s less influenced by muscle mass than creatinine, SDMA can reveal declines in GFR earlier. This makes it a useful marker for monitoring changes in GFR over time.

BUN can be affected by hydration and protein intake, so it’s less specific for early GFR changes. Creatinine clearance does reflect GFR but requires urine collection and calculations, and serum creatinine can be influenced by muscle mass. Urine specific gravity reflects concentrating ability and hydration status, not GFR directly.