The direct and indirect costs of axial spondyloarthritis (axSpA) in Singapore

OBJECTIVE: To estimate the economic annual direct and indirect costs of axial spondyloarthritis (axSpA) in Singapore, and to identify factors associated with these costs. METHODS: A retrospective, cross-sectional, Institutional Review Board-approved study was conducted. A questionnaire was administered to the patients between 2013 and 2016 from the Singapore General Hospital (SGH) spondyloarthritis registry. Direct medical costs and indirect costs were estimated using the SGH database and the human capital approach respectively. Multivariate analyses using generalized linear model with gamma distribution and a log-linked function was conducted to identify factors associated with these total, direct and indirect costs. All costs were adjusted to 2017 using the Singapore Consumer Price Index and converted to 2017 US dollars (USD) by purchasing power parity. RESULTS: A total of 135 consecutive patients were included in the study, with a mean age of 40.4 ± 13.2 years. The overall annual total economic cost to society was around USD 74 790 820, with annual direct cost being the main component of total cost (90.8%). Annual direct cost was around USD 67 931 457, while annual indirect cost was around USD 6 855 951. Presence of extra-spinal symptoms (ever) was associated with an increase in total and direct costs. Higher education level and Patient Global Assessment were associated with an increase in indirect costs. Lack of employment was associated with a decrease in indirect costs. CONCLUSION: The disease burden of axSpA in Singapore is not trivial given that the disease is relatively common. This highlights the need for measures to accommodate patients with axSpA economically in Singapore.