Background Efficacy of Tumor Necrosis Factor (TNF)-inhibitors in treatment of rheumatoid arthritis (RA) measured in randomized controlled trials (RCTs) may not be fully generalizable to routine care owing to the stringent inclusion criteria [1].

Objectives The objective of this study was to observe the effectiveness of TNF-inhibitors in Finland and to assess the real-world patients' potential eligibility for the RCTs.

Methods RA patients starting a TNF-inhibitor as their first, second or third biologic treatment between 2004 and 2014 were identified from the National Register for Biologic Treatment in Finland (ROB-FIN), which is an observational cohort study. Effectiveness was measured using the American College of Rheumatology (ACR) and European League Against Rheumatism (EULAR) response criteria and as the proportion of patients reaching Disease Activity Score 28 (DAS28) remission. Logistic regression was employed to identify any predictors of achieving EULAR response. The patients' baseline characteristics were compared against the inclusion criteria of 28 RCTs identified from two systematic reviews [2,3]. Treatment responses measured in the RCTs were compared to those achieved by routine care patients either eligible or not eligible for the same RCTs.

Results Of the 4067 TNF-inhibitor treatment periods, 2259 periods from 1899 patients with valid baseline visit were included in this study. The included patients were predominantly female (73%) with a median age of 55. Adalimumab, etanercept infliximab, golimumab and certolizumab pegol accounted for 41%, 40%, 9.7%, 5.1% and 4.6% of the medication periods, respectively.

Moderate and good EULAR responses at 6 months were achieved by 69% and 40% of the users of the first biologic drug, respectively. ACR20, ACR50 and ACR70 responses were reached by 47%, 25% and 13%, respectively. DAS28 remission was reached by 45%. Concomitant use of methotrexate (MTX) was associated with higher odds of achieving at least moderate EULAR response (odds ratio 1.8, 95% confidence interval 1.1– 3.0) as compared to TNF-inhibitor monotherapy. Golimumab and certolizumab pegol were possibly more effective than infliximab, depending on whether the discontinuers were included in the analysis or not.

Only 3.8% to 50% of the patients would have been eligible for the included RCTs. The eligible patients had generally better ACR50 responses as compared to the non-eligible ones.

Conclusions Different TNF-inhibitors were mostly equipotent in routine clinical practice, but the use of MTX co-therapy had a major influence on treatment response. The efficacy of TNF-inhibitors measured in RCTs cannot be directly generalized into Finnish routine healthcare.