BACKGROUND: Immunoglobulin (IG) replacement therapy, administered intravenously (IVIG) or subcutaneously (SCIG), is standard first-line treatment for most forms of primary immunodeficiency diseases (PIDD) with defective antibody production. SCIG allows for home administration of highly concentrated 20% IG or facilitated 10% IG delivered with recombinant human hyaluronidase. Limited data exist regarding characteristics of patients with PIDD initiating IVIG and SCIG.
OBJECTIVE: To identify and describe demographic, clinical, and treatment characteristics of patients with PIDD in the United States initiating IVIG and SCIG.
METHODS: This claims-based cohort study identified patients initiating IVIG or SCIG from 2012 to 2018, via diagnosis codes, in IBM MarketScan Research Databases. Clinical and demographic characteristics were documented and described for IVIG and SCIG initiators. Risk Vital Sign (RVS)--a claims-based weighted algorithm for PIDD risk--was used to assess disease severity.
RESULTS: The study population comprised 15,327 IVIG (57% female; median age 54 years) and 2604 SCIG initiators (69% female; median age 48 years). SCIG initiators, versus IVIG initiators, were more likely to have comorbidities such as asthma (59% vs 38%), chronic obstructive pulmonary disease (71% vs 58%), fibromyalgia (25% vs 20%), or inflammatory bowel disease (12% vs 8%), but were less likely to have cancer (11% vs 22%), coronary artery disease/hypertension (45% vs 58%), or peripheral vascular disease (11% vs 16%). SCIG initiators, versus IVIG initiators, also had greater use of high potency oral antibiotics (37% vs 31%) but less use of intravenous antibiotics (23% vs 29%), systemic high-dose corticosteroids (53% vs 67%), antifungals (25% vs 29%), and growth factors (1% vs 10%). Markers of disease severity differed: a greater proportion of IVIG initiators, compared with SCIG initiators, had RVS-predicted risks in the medium/high range (46% vs 37%) and pneumonia (29% vs 23%), while recurrent sinusitis was less common (38% vs 59%).
CONCLUSIONS: This exploratory analysis suggests differences between characteristics of patients with PIDD who initiated SCIG versus IVIG with respect to comorbidities, markers of PIDD severity, and previous PIDD treatments. Misclassification of PIDD status was possible, which warrants further research.
