Effect of microaggregate blood filtration on granulocyte concentrates in vitro

To determine the effect of transfusing granulocyte concentrates through microaggregate blood filters, granulocytes prepared with a cell processor were passed through screen and depth microaggregate filters. Pre- and postfiltration evaluations were made of total granulocyte count, levels of muramidase, granulocyte viability, motility, phagocytosis, bactericidal activity, and hydrogen peroxide-forming capacity. Compared to prefiltration levels, a significant (p less than 0.05) decrease in postfiltration granulocyte counts was seen for all the depth filters studied but not for the standard 170 microns (control) or the 40 microns screen filter. For the various tests of granulocyte function evaluated prefiltration, no significant postfiltration differences (p greater than 0.05) were seen for any of the filters studied. Screen microaggregate filters retained only 1 to 3 percent of granulocytes contained in the concentrates, and thus appear satisfactory for use in clinical transfusions. The large percentage of neutrophils retained by the depth filters (20-62%), however, precludes their use for transfusion of granulocyte concentrates.