Characterization of direct antiglobulin test‐negative autoimmune hemolytic anemia: A study of 154 cases

Direct antiglobulin test (DAT)-negative (DAT-)autoimmune hemolytic anemia (AIHA) is empirically thought to show the same clinical conditions as DAT-positive (DAT+)AIHA, with the exception of an adequate amount of red blood cell (RBC)-bound immunoglobulin (Ig)G. We investigated the clinical characteristics of DAT-AIHA in comparison with DAT+AIHA. Of the 582 patients referred to our laboratory with undiagnosed hemolytic anemia, AIHA was clinically diagnosed in 216 patients (DAT-AIHA, n = 154; DAT+AIHA, n = 62). The percentage of reticulocytes, mean corpuscular volume, RBC-IgG levels, white blood cell count, and total protein (TP) levels were significantly higher in patients with DAT+AIHA than patients with DAT-AIHA. The hemoglobin level was significantly lower in patients with DAT+AIHA. No significant differences between patients with DAT-AIHA and DAT+AIHA existed with respect to age, gender, idiopathic/secondary nature, complications such as Evans syndrome, effectiveness of steroid treatment, or survival rate at 1 year following diagnosis. Patients with DAT-AIHA required significantly lower doses of steroids for maintenance therapy. Based on multivariate analysis of idiopathic DAT-AIHA (n = 110), TP and Evans syndrome were associated with the effectiveness of steroids (adjusted odds ratio aOR, 1.36/0.1 g/dl; 95% confidence interval CI, 1.01-1.84) and survival at the 1-year follow-up (aOR, 0.1; 95% CI, 0.01-0.88). Our results indicate that patients with DAT-AIHA generally suffer milder anemia and hemolysis than patients with DAT+AIHA, respond equally well to steroids, and have comparable survival at 1-year.