[Clinical characteristics and prognosis of patients with direct antiglobulin test-negative autoimmune hemolytic...

Objective: To investigate the clinical characteristics and outcomes of direct antiglobulin test (DAT) -negative autoimmune hemolytic anemia (AIHA) and to provide evidence for the clinical diagnosis and management of this subtype. Methods: This was a single-center retrospective cohort study. Thirty patients with DAT-negative AIHA who were treated at the Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences, between January 2014 and December 2023 were included. All included patients tested negative by the microcolumn gel method using both polyspecific and monospecific antiglobulin reagents, and those with other causes of hemolytic anemia were rigorously excluded. The patients' baseline laboratory parameters, outcomes, and treatment responses were analyzed. Results: A total of 30 patients with DAT-negative AIHA were included, accounting for 4.77% of all patients hospitalized with AIHA during the same period; 20 (66.7%) were female and 10 (33.3%) were male; 26 (86.7%) had primary AIHA and 4 (13.3%) had secondary AIHA cases. The age at diagnosis was (44.8±17.8) years. The nadir hemoglobin level at disease onset was (61.3±15.9) g/L. The overall response rate to first-line glucocorticoid therapy was 93.3% (28/30), and rituximab was the most commonly used second-line treatment. Both patients who failed to respond to glucocorticoids achieved remission following salvage treatment with ibrutinib plus rituximab and cyclosporine plus rituximab. At a median follow-up of 64 months, the all-cause mortality rate was 10.0% (3/30). The median event-free survival (EFS) was 17.0 months, with 1-, 3-, and 5-year EFS rates of 56.5%, 45.9%, and 37.5%, respectively. Relapses were mainly triggered by drug tapering (73.7%) and infection (21.1%) . Conclusion: After a comprehensive diagnostic workup to exclude other causes and immunoglobulin A (IgA) - or IgM-mediated AIHA, patients with DAT-negative AIHA generally have a relatively favorable prognosis and show good responses to glucocorticoids, rituximab, and other immunosuppressive therapies.