Increased non-transferrin bound iron in plasma-depleted SAG-M red blood cell units

Background and Objectives Non-transferrin bound iron (NTBI) is associated with increased morbidity in a number of transfusion-dependent disease states such as the severe haemoglobinopathies. We hypothesized that this may be related to excess NTBI present in plasma-depleted red blood cell units that are free of clear haemolysis. Materials and Methods The level of NTBI was determined using the bleomycin assay in samples from 20 stored plasma-depleted red cell units, at approximate 5-day intervals up to day 33 after donation. Forty units of fresh-frozen plasma (FFP) and 40 units of platelet concentrates were used as negative controls, and samples from 12 units of FFP were also serially assessed. Results Median [interquartile range (IQR)] NTBI was 0 µm (0–0·35) in samples taken from units 3–10 days after donation. Thereafter, the levels of NTBI increased, becoming significant (median 3·05; IQR: 0·05–6·7 µm) 17–22 days after donation. After 30 days, NTBI was detectable in all red cell units. NTBI was undetectable in platelet concentrates and FFP. Conclusions Increased levels of NTBI become detectable 17–22 days after donation and increase further with storage time. This excess NTBI may promote bacterial infection in iron-loaded individuals.