Background EULAR guidelines for the treatment of rheumatoid arthritis (RA) patients (pts) using biological disease-modifying antirheumatic drugs (bDMARD) state that these should be combined with methotrexate (MTX) or other conventional synthetic DMARDs (csDMARD) since this combination has greater efficacy than monotherapy with most biological agents. However, our analysis of a sample of 14,543 bDMARD pt records suggests that on average, 23% of pts are treated without a csDMARD.
Objectives The aim of our analysis is to understand the clinical characteristics that may influence physicians' decision to use bDMARDs without a concomitant csDMARD to better understand current treatment strategies and what guidance can be given to physicians to optimise pt outcomes.
Methods We used data collected as part of an online treatment survey conducted among a panel of 240 rheumatologists between January and December 2013 across five EU countries (France: 48 dr, Germany: 53 dr, Italy: 52 dr, Spain: 42 dr and the UK: 45 dr) and ran a logistic regression analysis using a sub-sample of 5,200 pt records. The model uses pts' current treatment regimen (monotherapy or combination therapy) as a dependent variable, splitting the sample evenly between both groups. A number of pt characteristics are analysed (e.g. disease activity score (DAS), overall joint count, perceived disease severity at diagnosis and latest consultation (assessed by physician), ability to work and current co-morbidities), only pt cases with complete information for all 17 of these independent variables were included.
Results Our analysis shows that combination therapy is more likely to be chosen for pts with moderate to severe disease at diagnosis, those currently suffering from fibromyalgia or osteoarthritis, pts currently treated with steroids or those for whom biologic therapy was chosen to inhibit radiographic progression and provide long-term efficacy. At the same time, pts with a currently more severe disease (both perceived and as indicated by DAS) along with older patients are more likely to be treated with biologic monotherapy. This is also true for pts who's bDMARD was chosen to improve their quality of life and control flare-ups in their disease. Significant differences in the importance of these factors have been observed between the various bDMARD agents.
Our final model is statistically significant (χ2(4)=520.161, p<0.0005) and explains 13% (Nagelkerke R2) of the variance in treatment regimens. It correctly classifies 63% of cases and produces a sensitivity score of 64% and a specificity score of 61%. The positive predictive value of the model is 62% while its negative predictive value is 63%. Our iterative approach to the creation of the model means that it only includes predictor variables that are statistically significant. As a result the Hosmer and Lemeshow test is not statistically significant (p=0.945), indicating that the model is a good fit for the data.
Conclusions While our model fits closely with the pts and treatment data we tested, it only explains a small proportion of physicians' choice to prescribe bDMARD monotherapy over the potentially more efficacious combination option. As a result, there is a need to better understand physicians' decision processes in order to provide improved guidance on the use of bDMARD monotherapy and ensure that pt outcomes are optimised.
Disclosure of Interest None declared