Monitoring of iron requirements in renal patients on erythropoietin

We studied 38 patients (9 haemodialysis, 18 peritoneal dialysis, 11 advanced renal failure) over the first 12 weeks of erythropoietin therapy. In 14 iron-overloaded patients (ferritin >500 μg/l) the haemoglobin (±SEM) increased from 6.74±0.27 to 9.85±0.36 g/dl (P<0.0001) entirely by mobilizing iron reserves (reduced from 1, 220±73 to 739±111 mg, P<0.0001). In the 24 non-overloaded patients (ferritin<500 μg/l) the haemoglobin rose similarly from 7.04±0.18 to 10.70±0.36 g/dl (P<0.0001), partly from iron reserves (depleted from 200±74 to −44±77mg, P=0.016) and partly from oral iron supplements (305±110 mg). In the overloaded patients the ferritin declined from 1057 μg/l (geometric mean, range 504–3699) to 317 μg/l (42–1505, P<0.0001). In the non-overloaded patients it declined from 82 μg/l (8–461) to 45 μg/l (5–379, P=0.016). The transferrin saturation (TS) in the overloaded patients appeared to decline from 38.3±7.2% to 24.0±3.7% but this was not statistically significant. In the non-overloaded the TS was unchanged (23.3±2.4 before and 28.1±3.6% after treatment). Considering all 38 patients together, the haemoglobin correlated negatively with the ferritin (r=0.3731, P<0.001) but not with the TS. The TS correlated with the serum ferritin initially (r=0.75, P<0.001) but not after the first 4 weeks. At 12 weeks, eight of 15 patients with iron deficiency (ferritin<50 μg/l) had a TS >20%, whereas two of five patients with persistent iron overload (ferritin >500 μg/l) had a TS <20%. We conclude that (a) in patients with iron overload, stored iron is utilizable for erythropoiesis; (b) oral iron supplements are necessary and sufficient for most patients without iron overload; (c) the serum ferritin is a better indicator of iron status than the TS for renal patients on erythropoietin.