Table 2 Non-GFR determinants of blood creatinine and cystatin C concentrations

GFR overestimation due to decreased creatinine or cystatin C

Physiologic factors:

Physiologic factors:

unknown

unknown

Pathologic conditions:

Pathologic conditions:

amputation, frailty, anorexia, sarcopenia, liver cirrhosis, thyroid disease, chronic illness, critical illness; extra-renal elimination e.g.intestinal bacterial metabolism, spinal cord injury and progressive neuromuscular disease

thyroid disease

Diet:

Diet:

vegan diet

unknown

GFR underestimation due to increased creatinine or cystatin C

Physiologic factors:

Physiologic factors:

high muscle mass e.g. bodybuilders

smoking, lower lean body mass

Pathologic conditions:

Pathologic conditions:

obesity, rhabdomyolysis, thyroid disease

Obesity, diabetes, inflammation, thyroid disease, hypercortisolism

Diet:

Diet:

high meat consumption, creatine supplements

unknown

Drugs:

Drugs:

Inhibition of tubular secretion- trimethoprim, cobicistat, dolutegravir, fenofibrate, olaparib, ritonavir, cimetidine

glucocorticoids