Use of polyethylene glycol (PEG) to promote adsorption of autoantibodies is reported to give good recovery of concomitant alloantibodies. In initial experiments, PEG and ZZAP (Ficin and DTT) adsorption procedures were compared for removal of autoantibody and recovery of alloantibody. Postadsorption studies (n = 11) were performed and hemagglutination scores compared. In subsequent studies, equal volumes of alloantibody containing sera, PEG, and antigen-negative red blood cells (RBCs) were used in twofold adsorption experiments. Saline was substituted for PEG for control purposes. Postadsorption titers and immunoglobulin levels were determined. Autoantibodies were completely removed by both methods (n = 5); better by PEG (n = 3); better by ZZAP (n = 1); and not adsorbed (n = 1), and partially adsorbed by both (n = 1). Alloantibody recovery was comparable in three cases (E, K, Jka) but weaker by at least one reaction grade in four (K,E, Jka, and antibody to low-frequency antigen). The latter anti-Jka reacted 1+ with Jk(a+b+) RBCs after ZZAP adsorption but was nonreactive with the same RBCs following PEG adsorption. Titers of six alloantibodies adsorbed with antigen-negative RBCs in PEG were markedly weaker (range 2 to 8) compared to saline controls (range 4 to 32). IgG levels for PEG adsorbed (range 128 to 243 mg/dL) were 50% lower than controls (range 265 to 505 mg/dL). Although PEG adsorption is effective in removing autoantibody, the precipitation of immunoglobulin by PEG may result in failure to detect underlying alloantibody. Immunohematology 2001;17:82–85.
