Background The treatment of ankylosing spondylitis (AS), psoriatic arthritis (PsA), and rheumatoid arthritis (RA), collectively referred to as Immune-Mediated Rheumatoid Disease (IMRD), has evolved in recent years with the introduction of subcutaneous TNF-alpha inhibitors (SC-TNFi).

Objectives The aims of this study were: i) To assess real-world persistence in SC-TNFi naïve and experienced patients treated with SC-TNFi for IMRD in Sweden; and ii) to estimate and compare health care resource utilization (HCRU) costs in these two patients populations.

Methods This study was a retrospective, observational register analysis of treatment patterns and costs based on anonymized patient-level data extracted from Swedish national health data registers. Patients (≥18 years old) were identified through filled prescriptions for adalimumab, etanercept, certolizumab pegol, and golimumab between 5/6/2010 and 12/31/2012 from the Swedish Prescribed Drug Register. Information on prescriber specialty and department was used to exclude patients initiating treatment with SC-TNFi for diseases other than IMRD. Patients were excluded if they filled at least one prescription from a department other than rheumatology, orthopedics or rehabilitation and if the prescription was issued by a non-rheumatologist. The included patients were classified by diagnosis as AS, PsA, RA, “other arthritis”, or “unknown”. To enhance comparability, propensity score matching (PSM) was implemented. Patients were matched based on age, gender, index year, diagnosis, therapy, Charlson Comorbidity Index, and non-biologic DMARD use. Persistence was estimated using non-parametric survival analysis. Health care resource utilization (HCRU) was captured 12 months after treatment initiation and comprised specialized outpatient care, inpatient care, and non-DMARD medication.

Results A total of 5,748 patients were identified (treatment naïve – 1st line: 4,903, treatment experienced – 2nd line: 845). A successfully balanced PSM cohort was generated with 839 matched pairs. Comparisons over the study period showed that patients initiating their first line of treatment had significantly higher persistence than patients initiating their second line of treatment with SC-TNFis (p<0.001). HCRU was evaluated for a subset of 393 matched pairs, where both patients were persistent for at least six months. In the twelve months post treatment initiation, patients on first line therapy incurred lower mean total costs than patients on second line therapy (USD 3,206 vs. 4,540, p<0.001).

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Conclusions SC-TNFi-naïve IMRD patients initiating treatment had significantly higher persistence rates than patients initiating a second line of treatment with SC-TNFis in Sweden. In addition these patients also incurred significantly lower mean total HCRU costs twelve months post treatment initiation. These results indicate that it may be advisable to prescribe the SC-TNFi which has demonstrated best long-term persistence as first line SC-TNFi. It appears especially important for indications which have fewer choices of approved biologics.

Disclosure of Interest J. Dalen Consultant for: Merck, A. Svedbom Consultant for: Merck, C. Black Employee of: Merck, S. Kachroo Employee of: Merck