The conundrum of serum ferritin measurement in patients with chronic kidney disease.

Serum ferritin level, the most commonly used marker for determining iron status in patients with chronic kidney disease, is influenced by factors such as inflammation and malnutrition. Moreover, there seems to be considerable biological variability and analytical variation between different serum ferritin assays. This Practice Point commentary discusses a recent paper by Ford et al. that examined the interassay differences and short-term intraindividual variability of serum ferritin measurements in patients on chronic hemodialysis. A comparison of six commonly used serum ferritin immunoassays revealed intermethod variation of up to 337 pmol/l among hemodialysis and nonhemodialysis patients. The intraindividual coefficients of variation for serum ferritin level in 60 stable hemodialysis patients ranged from 2% to 62% over an initial 2-week period and from 3% to 52% over a 6-week period. This commentary discusses Ford et al.'s paper and supports the conclusion that nephrologists should not use a single serum ferritin value to guide intravenous iron treatment in patients on chronic hemodialysis.