Epidemiology of Hospitalizations Due to Autoimmune Hemolytic Anemia in the United States

Introduction:

Autoimmune hemolytic anemia (AIHA) is an acquired immune disorder resulting in the production of cold and warm autoantibodies directed against red blood cell antigens; characterized by shortened red blood cell survival and a positive Coombs test. Types include primary disease (idiopathic) or secondary to other autoimmune disorders, malignancies, or infections. Treatment involves immunosuppression with corticosteroids and other agents, Transfusion. There is not much recent data available on epidemiology of AIHA. We aim to estimate epidemiological trends and outcomes of AIHA as well as factors associated with poor outcomes by using the largest available national database from the United States.

Methods:

We derived a study cohort from the National Inpatient Sample (NIS) for the years 2007-2018 for hospitalizations due to AIHA by using International Classification of Diseases (9th/10th Editions) Clinical Modification diagnosis codes ICD-9-CM/ICD-10-CM). Other diagnosis and comorbidities were also identified by ICD-9/10-CM codes and Elixhauser comorbidity software. Our primary outcome was discharge disposition following AIHA hospitalization. We utilized multivariable survey logistic regression models to analyze and identify predictors of poor outcomes.

Results:

Between 2007-2018, a total of 52,814 hospitalizations occurred due to primary diagnosis of AIHA. Burden of hospitalizations remained stable from 4,254 (8.1%) in 2007 to 4,405 (8.3%) in 2018. AIHA patients in the study cohort were mostly above 65 years of age (48.6%) followed by 35-65 years of age (33.7%), females (58.3%) and Caucasians (69.1%). Overall in-hospital mortality of AIHA hospitalizations was 3.1%, and discharge to facility was 11.86%. Median length of stay for AIHA hospitalization was 4-days (interquartile range: 2-days to 6-days). Furthermore, in multivariable logistic regression analysis, increasing age (OR 1.2; 95%CI 1.1-1.3; p<0.001), male gender (OR 1.5; 95%CI 1.2-1.3; p:0.0024), vascular events (OR 1.5 ; 95%CI 1.1-2.0; p:0.0156), teaching hospitals (OR 3.1; 95%CI 1.5-6.5; p:0.002), plasmapheresis (OR 5.5; 95%CI 2.8-10.8; p:0.001) and intravenous immunoglobulins (OR 1.9; 95%CI 1.3-3.0; p:0.001) were associated with higher in-hospital mortality.

Conclusion:

Our study describes the epidemiology of hospitalizations due to AIHA in the United States from a nationally representative database. We observed that hospitalization burden due to AIHA have remained stable from 2007 to 2018. We also identified factors associated with higher in-hospital mortality and some of which are modifiable. Further studies are required to establish the causal association of these factors to poor outcomes and develop better risk stratification strategies to improve overall outcomes of AIHA.