IgA content of frozen-thawed-washed red blood cells and blood products measured by radioimmunoassay.

The IgA concentration of various blood products was examined by a radioimmunoassay, and the lowest IgA concentrations were seen in frozen-thawed-washed red blood cells. The routine Regional Blood Transfusion Centre preparation contained a mean IgA concentration of 0.117 mg/l (n=21) in the frozen-thawed-washed red blood cell supernatant fluid. Further washing of frozen-thawed-washed red blood cells with saline reduced supernatant IgA concentrations to below the limit of IgA detection (less than 0.003 mg/l). Ordinary washed red blood cells and other blood plasma fractions contained substantial quantitites of IgA, supporting the view that frozen-thawed-washed red blood cells should be used for transfusion of patients at risk of developing reactions to IgA, and the need for caution in the use of other blood products in such patients.