Serum non-transferrin-bound iron (NTBI) levels assessed at arbitrary time points during transfusion cycles may not be representative if NTBI is undergoing significant changes during transfusion cycles. In 15 patients with beta-thalassemia major (age: 21 +/- 6 years, liver iron concentration: 2200 +/- 1200 microg/g-liver), NTBI and other hematologic parameters (transferrin saturation, transferrin receptor) were measured weekly. The largest variation of NTBI levels between individual patients was observed at midcycle. For long-term monitoring of NTBI levels, a particular time point relative to the last blood transfusion should be selected for blood drawing.
