Presenting hemoglobin levels (g/dL) in 308 patients with primary AIHA. The grouped histogram is a visualization of data presented by Barcellini et al.⁸  Different AIHA types were defined as follows: warm AIHA: DAT+ for IgG (with or without C3d); cold AIHA: DAT+ for C3d only with I-specific cold agglutinins at titer ≥64; mixed AIHA: DAT+ for IgG and C3d, with coexisting warm and high-titer cold autoantibodies; atypical AIHA: DAT−, or DAT+ for IgA only, or warm IgM, or mitogen-stimulated DAT+ only.