Creatinine-based eGFR depends on how much creatinine the body makes, not only on how fast the kidneys clear it. This Kidney International commentary discusses a newly identified variant in the glycine amidinotransferase (GATM) gene, specific to African ancestry, that increases creatine synthesis and so serum creatinine — without any change in measured kidney function.
The finding offers a biological explanation for part of the bias that persists in creatinine-based equations for people of African ancestry, and illustrates the general point that non-renal factors can move creatinine.
The variant itself is unlikely to matter for most Indian patients. The broader lesson does: muscle mass, diet, liver disease and genetics all shift creatinine, and when the number does not fit the patient, a second marker helps.
- Remember that creatinine reflects production as well as clearance.
- Consider cystatin C when a creatinine-based eGFR does not fit the clinical picture.
- Be cautious with creatinine-based eGFR at extremes of muscle mass and in liver disease.
- This variant is specific to African ancestry; its relevance to Indian patients is limited.
Why it matters
A genetic cause of high creatinine with normal kidney function shows how easily eGFR can mislabel CKD.
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