In vitro studies of the impact of transfusion on the detection of alloantibodies after autoadsorption.

BACKGROUND

In a patient with warm autoantibodies who has recently received a transfusion, it is not recommended to perform adsorptions using autologous RBCs to detect alloantibodies. Although not scientifically documented, this position is based on the theory that transfused RBCs in the patient's circulation would be capable of adsorbing alloantibodies that may be present. This in vitro study was designed to determine what percentage of transfused RBCs might completely remove alloantibodies in vivo.

STUDY DESIGN AND METHODS

Selected D, E, K, Fy(a), and Jk(a) antibodies were adsorbed with mixtures of antigen-positive and antigen-negative RBCs to determine the lowest concentration of antigen-positive RBCs capable of removing all alloantibody reactivity. The percentage of antigen-positive RBCs in each mixture was determined by flow cytometry.

RESULTS

Small amounts of antigen-positive RBCs (2-6%, as determined by flow cytometry) completely removed anti-D, -E, and -Fy(a) reactivity. Reactivity of two examples of anti-K was removed by 11 percent and 17 percent of K+ RBCs, respectively. Anti-Jk(a) reactivity was completely removed by 4 to 5 percent Jk(a+) RBCs using a PEG adsorption; the endpoint (>11%) was estimated, but complete adsorption with ZZAP-treated RBCs was not performed.

CONCLUSION

Small amounts of antigen-positive RBCs are generally capable of removing all alloantibody reactivity. Thus, waiting for 3 months after transfusion before performing autologous adsorptions is a prudent policy.