Moderately increased serum concentrations of total IgG in CPB patients over the observation period. Serum IgG concentrations were determined by ELISA before (d0), 10 days (d10), and > 4 months after CPB. The Friedman test with a Dunn posttest revealed significant increases of IgG over time in all patients (A), with no major difference in the pattern between nonresponder (B) and responder (C) groups. However, the mean value for IgG in responders to PF4/H at baseline was lower than in nonresponders. This was because of a larger proportion of patients with total IgG levels > 15 mg/mL (see also supplemental Figure 2; n = 166). ***P < .001.