Primary immunodeficiency disease: A cost-utility analysis comparing intravenous vs subcutaneous immunoglobulin replacement therapy in Australia

Background - Hospital-based intravenous immunoglobulin (IVIg) treatment has been the standard treatment mode for patients with primary immunodeficiency disease (PID). With the newer home-based subcutaneous immunoglobulin (SCIg) becoming approved for use in most countries, the question arises as to whether SCIg is a cost-effective treatment mode compared to IVIg in Australia. Materials and methods - We developed a Markov cohort simulation model with six health states: PID without infection, PID with infection treated at home or hospital, bronchiectasis without infection, bronchiectasis with infection treated at home or hospital, bronchiectasis with chronic Pseudomonas aeruginosa infection, and death, from an Australian healthcare system perspective. A 10-year time horizon with weekly cycles was chosen, and the expected costs and quality-adjusted life-years (QALYs) of the two treatment options estimated. Results - The cumulative 10-year cost per patient was 297,547 Australian dollars (A$) with IVIg and A$ 251,713 for SCIg. IVIg resulted in 5.55 QALYs and SCIg 5.57 QALYs. Thus, SCIg appears to be a cost-saving option and possibly improves QALY from the Australian healthcare system perspective (i.e., the dominant treatment option). A probabilistic sensitivity analysis showed that the SCIg option is preferred in 93.2% of simulations given willingness to pay of A$ 50,000 per QALY gained. Discussion - The results suggest that home-based SCIg is a cost-effective treatment option for patients with PID in Queensland, Australia.