Health Resource Utilization Among Patients with Warm Autoimmune Hemolytic Anemia in Sweden: A Retrospective Registry-Based Study
Authors: Kjellander Christian , Crivera Concetta , Leon Ann , Cai Qian , Jacob Tina , Zeng Erwei , Jones Christina V , Leval Amy , Fitzgibbon Marie , Noel Wim , Shu Cathye , Larfors Gunnar 
Published: December 2024

Background
Warm autoimmune hemolytic anemia (wAIHA) is a rare and severe disorder characterized by autoantibody-mediated red blood cell hemolysis. wAIHA management is challenging as it impacts a heterogeneous patient population, has limited effective treatment options and an increased risk of mortality.
Aim
This study describes the healthcare burden associated with wAIHA in Sweden.
Methods
Patients diagnosed with wAIHA between July 2005 and June 2023 were identified using linked population-based health registers. wAIHA was classified as primary or secondary based on the presence of associated underlying diseases (hematologic malignancies, autoimmune diseases, primary immunodeficiencies, infection, transplantation) within ±180 days of wAIHA diagnosis. All-cause specialized healthcare resource utilization (HRU; inpatient admissions (IP) and outpatient visits (OP)) and direct medical cost (based on diagnosis-related group codes capturing hospital-based treatment and care cost) were reported as average per-patient-per-year (PPPY); defined as visit count, total time in care or total cost divided by total patient-time in first year post-diagnosis and as an annualized average across the subsequent 3-year follow-up period.
Results
We identified 431 patients aged ≥18 years with a main diagnosis of wAIHA in the Swedish Patient Register. 273 patients with primary wAIHA and 139 patients with secondary wAIHA were included. 19 patients with Evans Syndrome were excluded. Average age at diagnosis for primary and secondary wAIHA was 65.3 (SD: 19.0) and 72.1 years (SD: 13.2), respectively, and 52% and 53% were male, respectively. Hematological malignancies were the most common underlying condition associated with secondary wAIHA (74%).
Patients with wAIHA had significant ongoing need for specialized healthcare. All patients accessed specialized care (IP and/or OP) in the first year post-diagnosis, and continued care was required in the second, third, and fourth follow-up year by 87%, 81% and 78% of patients with primary wAIHA and 98%, 98% and 90% of patients with secondary wAIHA.
Patients with primary wAIHA had on average 11 specialized care occasions PPPY in the first year post-diagnosis and 6 specialized care occasions PPPY in the subsequent 3 follow-up years. Inpatient care was required by 65% and 45% of patients with primary wAIHA in the first year post-diagnosis and the subsequent 3 years, respectively. Emergency care was required by 25% of patients with primary wAIHA in the first year post-diagnosis and by 27% in the subsequent 3 years. Overall, patients with primary wAIHA spent 21 days PPPY in specialized care during the first year post-diagnosis (60% of this time in IP) and 10 days PPPY during the subsequent 3 years (46% IP).
Patients with secondary wAIHA had on average 17 specialized care occasions PPPY in the first-year post diagnosis and 9 specialized care occasions PPPY in the subsequent 3 follow-up years. Inpatient care was required by 81% and 71% of patients with secondary wAIHA in the first year post-diagnosis and the subsequent 3 years, respectively. Emergency care was required by 35% of patients with secondary wAIHA in the first year post-diagnosis and by 44% in the subsequent 3 years. Overall, patients with secondary wAIHA spent 38 days PPPY in specialized care during the first year post-diagnosis (68% of this time in IP) and 18 days PPPY during subsequent 3 years (63% IP).
The ongoing need for IP admissions and OP visits translated to high direct medical cost for specialized care. Annual average cost (IP+OP) for patients with primary wAIHA was €13,993 / $15,131 PPPY in the first year post-diagnosis and €7,186 / $7,770 during subsequent follow-up years. For patients with secondary wAIHA, annual average cost (IP+OP) was €26,193 / $28,322 in the first year post-diagnosis and €11,956 / $12,928 during subsequent follow-up years. Median overall survival was 11.4 and 4.1 years for patients diagnosed with primary and secondary wAIHA, respectively.
Conclusion
This study highlights that management of both wAIHA subtypes is associated with significant long-term HRU - including ongoing need for emergency and inpatient care - and significant cumulative healthcare cost. High HRU in the first year after diagnosis and ongoing elevated HRU in subsequent years emphasizes that unmet medical need remains for more effective treatment options to improve outcomes and quality of life for patients with wAIHA.