Altered Filterability of CPD‐Stored Sickle Trait Donor Blood

Previous studies have shown that in sickle trait (AS) donor blood very little sickling is visible. AS donor blood was evaluated by a method of blood filtration, which would be sensitive to intracellular gellation of S hemoglobin which might not be evident morphologically. Blood was collected from normal and sickle trait subjects into CPD solution and stored at 4 C. Blood was removed over a 21‐day period and filtered through paper filters at unit gravity and also examined microscopically. Sickling was not evident in saline wet preparations, but was seen in each AS sample in 10 per cent formalin‐saline. At 4, 25, and 37 C, AS blood filtered less rapidly than did normal (P < 0.01). AS blood filterability became progressively prolonged as temperature rose; conversely normal blood filterability shortened with increasing temperature. Over 21 days, AS blood remained less filterable than normals. AS samples with high hemoglobin S percentages filtered significantly more slowly than did those with less S hemoglobin. Recognizing that these studies refer only to blood in vitro, no conclusions are drawn with respect to reversibility of the altered filterability or any possible clinical implications.