We used gel centrifugation tests (GCTs) to analyze the relationship between the diagnosis and immunohematology tests used for autoimmune hemolytic anemia (AIHA). The study included 588 samples positive for the direct antiglobulin test (DAT). Of these, 52 were from patients diagnosed with AIHA. Immunoglobulin (Ig) class, IgG1, IgG3, and complement were measured. DAT strength had the strongest correlation with AIHA diagnosis (odds ratio [OR], 23), followed by anti-IgG titer 300 (OR, 8.4), anti-IgG titer 1,000 (OR, 10.5), and C3d agglutination strength (OR, 1.7). Decision tree analysis revealed that DAT strength and anti-IgG titer higher than 100 were the best predictors of AIHA. Multidimensional scanning analysis found a high grade of similarity among DAT strength, anti-IgG titer, and IgG strength in the AIHA samples. This observation was not detected in DAT-positive samples from patients without AIHA. DAT strength remained the best diagnostic indicator for AIHA and had the strongest association with AIHA compared with other commercially available immunohematology tests. The other tests, despite good correlation with AIHA diagnosis, did not add useful information.