Introduction: Intravenous immunoglobulin (IVIG) has been shown to be effective in treating steroid-refractory dermatomyositis (DM). There remains no evidence of its cost-effectiveness in Thailand.

Objective: Our objective was to estimate the cost utility of IVIG as a second-line therapy in steroid-refractory DM in Thailand.

Methods: A Markov model was developed to estimate the relevant costs and health benefits for IVIG plus corticosteroids in comparison with immunosuppressant plus corticosteroids in steroid-refractory DM from a societal perspective over a patient’s lifetime. The effectiveness and utility parameters were obtained from clinical literature, meta-analyses, medical record reviews, and patient interviews, whereas cost data were obtained from an electronic hospital database and patient interviews. Costs are presented in $US, year 2012 values. All future costs and outcomes were discounted at a rate of 3 % per annum. One-way and probabilistic sensitivity analyses were also performed.

Results: Over a lifetime horizon, the model estimated treatment under IVIG plus corticosteroids to be cost saving compared with immunosuppressant plus corticosteroids, where the saving of costs and incremental quality-adjusted life-years (QALYs) were $US4738.92 and 1.96 QALYs, respectively. Sensitivity analyses revealed that probability of response of immunosuppressant plus corticosteroids was the most influential parameter on incremental QALYs and costs. At a societal willingness-to-pay threshold in Thailand of $US5148 per QALY gained, the probability of IVIG being cost effective was 97.6 %.

Conclusions: The use of IVIG plus corticosteroids is cost saving compared with treatment with immunosuppressant plus corticosteroids in Thai patients with steroid-refractory DM. Policy makers should consider using our findings in their decision-making process for adding IVIG to corticosteroids as the second-line therapy for steroid-refractory DM patients.