Fig. 1. Preoperative and postoperative antiaprotinin immunoglobulin (Ig)G antibody concentrations in all patients with measurable IgG concentrations. Although only patients with an optical density ratio greater than 3 were defined as positive for aprotinin-specific IgG antibodies, this figure includes all results with a measurable optical density. Patients experiencing an anaphylactic reaction to aprotinin reexposure are represented by the heavy lines and filled circles.