Although baseline SAP concentrations are partially genetically determined13, the significant correlation between SAP and haptoglobin concentrations (Pearson correlations (two-tailed) r=0.41, P<0.0001, r=0.33, P=0.004 for 96 males and 77 females, respectively; Supplementary Data 2) suggests that inflammation and/or infection are the probable drivers of this heterogeneity. Here, HP is linked to infection.