BackgroundWarm autoimmune hemolytic anemia (wAIHA) is clinically characterized by autoantibody-mediated (typically IgG) erythrocyte destruction at body temperature. While oral corticosteroids remain first-line therapy, rituximab is frequently used as a second-line agent, mostly supported with concomitant background medications, yet real-world evidence is limited and utilization is driven by published retrospective data and expert opinion. Real-world evidence characterizing its utilization patterns and outcomes is needed to inform clinical practice.

AimsThis study aimed to: 1) describe treatment patterns among patients with newly diagnosed wAIHA, 2) evaluate rescue therapy use and healthcare resource utilization (HCRU) with current standard of care (SOC), 3) characterize patterns of rituximab use during the first year.

MethodsNewly diagnosed wAIHA patients were identified from multiple US databases (MarketScan® Databases, IQVIA PharMetrics, Optum Clinformatics®, and Optum PanTher EHR). Patients with ≥1 wAIHA diagnosis code in any position (ICD-10-CM D59.11) from October 2020 to December 2023 and 12-month post-index follow-up were pooled together. Secondary wAIHA was defined with evidence of hematologic malignancy, solid tumors, immunodeficiencies, or autoimmune diseases in the 6 months prior to diagnosis. Patients on treatment were defined by use of oral corticosteroids (OCS), immunosuppressants (IST) (including azathioprine, mycophenolate mofetil, cyclosporine, cyclophosphamide, or tacrolimus) or rituximab. Initial therapy was defined as the first treatment occurring ≥ 30 days prior to diagnosis. Therapies were identified as combination when initialized within 21 days of each other. The regimen is considered active until all therapies are discontinued or a new agent is initiated. Rituximab regimens were classified as standard (4 weekly doses), alternative (2 doses given 2 weeks apart), single infusion, or extended (>4 infusions).

Results Among 2,028 wAIHA patients (median age 62.0 years, 59% female), 55% had secondary wAIHA. Among patients on treatment (n=1,439), 64% received OCS monotherapy; rituximab and IST, alone or in combination with OCS were received by an additional 28% and 5% of patients, respectively. Overall, 80% of treated patients received OCS in some combination during initial therapy. Within 12 months following diagnosis, 1 in 4 patients required ≥ 1 blood transfusion, 1 in 8 required either erythropoiesis-stimulating agents (ESA) or intravenous immunoglobulin (IVIG). Within 12 months of diagnosis, 35% of patients required ≥ 1 hospitalization, average length of stay 3.8 days; AIHA was the principal diagnosis for 65% cases. Greater than 1/3 of patients (38%) had ≥ 1 emergency department visit. Almost all wAIHA patients (98%) had an all-cause outpatient visit with a median of 31 visits per patient.

Among patients receiving rituximab in any line (n=613), median time from diagnosis to first administration was 59.0 days (interquartile range: 42.0-171.0). For the first course of rituximab, 62.2% of patients received a complete course (standard, alternative, or extended courses). Among patients with a completed course, 39.8% had >4 infusions without a 90-day gap between administrations with a median of 8 administrations within 12 months. Of the nearly 38% of patients that did not receive a complete course of rituximab, 33% received a single infusion.

The use of rescue medications in the period prior to rituximab treatment was compared to the period after treatment (defined as 60 days to 12-months post final rituximab infusion). Use of blood transfusions was observed to increase from 9.0% to 32.8%, while the use of ESA and IVIG were stable at approximately 2% and 4%, respectively.Conclusion With current wAIHA SOC, US HCRU remains high, posing a financial burden in terms of the rate of outpatient and emergency department visits, and inpatient stays. Rituximab is an early line therapy post-diagnosis, typically in combination with OCS. No changes in rescue treatments, and an increase in blood transfusions after rituximab infusion suggest treatment gaps remain. Analysis reveals heterogeneity in rituximab dosing patterns including high deviation from standard dosing practices; this variance from published expert opinion along with common use of rescue therapies suggests continued need for standardized guidelines and development of targeted therapies in wAIHA.

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2025
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