How Does Multimorbidity Impact On The Direct And Indirect Costs In Patients With Rheumatoid Arthritis?

Background: Comorbidities are prevalent in patients with rheumatoid arthritis (RA) and associated with worse outcomes as well as higher economic burden. Little is known about the impact of multimorbidity on the direct and indirect costs of RA. Evidence of the incremental scale of these multimorbidity costs will usefully inform RA interventions and policies. Objectives: The aim of this study was to describe how multimorbidity impacts on the cost-of-illness, including direct and indirect costs, in patients with RA. Methods: The Scottish Early Rheumatoid Arthritis (SERA) is a registry of patients newly presenting with RA since 2011. It contains data on patient characteristics, clinical outcomes, health-related quality of life, and employment status data. These data were linked to routinely recorded hospital admissions and primary care prescribing data. Direct costs were estimated by applying relevant unit costs to healthcare resource use quantities. Indirect cost estimates were obtained from information on employment status and hospital admissions, valued by age and sex specific wages. Two-part models (probit followed by generalized linear model) were used to estimate direct and indirect costs, adjusting for age, gender, and functional disability. The Charlson Comorbidity Index (CCI) score was calculated using patient ICD-10 diagnoses from hospital records. The number of comorbidities was categorized into “RA alone”, “single comorbidity” and “multimorbidity (>1 comorbidity)”. Results: Data were available for 1,150 patients, 65.7% were female and a mean age of 57.5±14 years. The majority of patients only had RA (54.1%), followed by a single comorbidity (23.4%) and multimorbidity (22.5%). Annual total costs were significantly higher for patients with multimorbidity (£6,669 95% CI £4,871-£8,466; OR 11.3 95% CI 8.14-15.87) and for patients with a single comorbidity (£2,075 95% CI £1,559-£2,591; OR 3.52 95% CI 2.61-4.79), when compared with RA alone (£590). The excess costs were mainly driven by direct costs (£6,281 versus £1,875 versus £556). Although the difference in indirect costs between patients with multimorbidity and a single comorbidity were not statistically significant (£1,218 versus £914, p=0.11), patients with multimorbidity were associated with significantly higher costs than those with RA only (£594, p Conclusion: The presence of comorbidity contributes significant excess to both direct and indirect costs among RA patients. In particular, patients with multimorbidity incurred substantially higher direct costs than those with a single comorbidity or RA only. Acknowledgements: The study analysed the data from the Scottish Early Rheumatoid Arthritis (SERA) study with a linkage to routinely recorded health data from Information Service Division, National Service Scotland. We would like to thank all the patients, clinical and nursing colleagues who have contributed their time and support to the study, the SERA steering committee for the approval, and Allen Tervit from the Robertson Centre for Biostatistics, University of Glasgow for the timely technical supports. Disclosure of Interests: Ping-Hsuan Hsieh: None declared, Claudia Geue: None declared, Olivia Wu Consultant of: OW has received consultancy fees from Bayer, Lupin and Takeda outside the submitted work., Emma McIntosh: None declared