Other Estimation of Blood Losses in Hemodialysis and Formula for Translating Liver Iron Concentration From Iron Balance Calculation Based on Iron Removal by Phlebotomy

To the Editor: In his recent editorial, Daniel Coyne raises concerns regarding iron overload detection in dialysis patients by quantitative magnetic resonance imaging (MRI). Using the equation established by Barry in 1974 (based on the relationship between liver iron content [LIC] and stored iron mobilized by phlebotomy in 12 patients with genetic hemochromatosis, where 30 mmol/g dry liver LIC equals 1 g of iron), Daniel Coyne calculates that the decline in LIC on MRI found by Rostoker et al. in their iron-overloaded hemodialysis patients after iron withdrawal (17.9 mmol/g dry liver/month or 215 mmol/ g dry liver per year) “cannot match blood losses (7.16 g of iron lost per year with Barry’s formula).” I recently conducted an in-depth review of blood loss in hemodialysis patients; these are related to the hemodialysis procedure itself, to routine blood sampling for laboratory tests, and to occult gastrointestinal bleeding due to uremic enteropathy. In dialysis patients with a native fistula, iron losses are 1340 mg per year compared with 2765 mg per year in patients with a long-lasting double-lumen catheter; these losses are increased by antiplatelet drugs and vitamin K antagonists (703–961 mg of additional iron lost). With the widely used formula of Brissot et al. (based on the relationship between LIC and phlebotomy in 29 cases of genetic hemochromatosis in which 130 mmol/g dry liver LIC equals 1 g of iron), the yearly decrease in LIC found by Rostoker et al. (270 mmol/g per year, corresponding to 1680 mg of iron per year) fits fairly well with usual blood losses in hemodialysis patients.