Which of the following is listed as a cause of disproportionately low creatinine?

• A. Overestimation of GFR
• B. Low muscle mass
• C. Liver failure
• D. Malnutrition

Answer: (A)

Creatinine-based estimates of GFR rely on a relatively stable creatinine production and its clearance by the kidneys. When the GFR is overestimated, the computed GFR is higher than the true filtration rate. In that situation, the actual creatinine level ends up looking lower than what would be expected for that inflated GFR, producing a pattern of disproportionately low creatinine relative to the estimated GFR.

Other factors like low muscle mass, liver failure, or malnutrition reduce creatinine production and can lower serum creatinine, but they don’t by themselves imply that GFR has been overestimated. The key idea here is that an overestimated GFR creates the mismatch where creatinine appears disproportionately low for the given (overestimated) GFR.