Figure 1.

Method used by the population model to calculate populations defined by disease categories. (A) Schematic showing how the model calculates the proportion of the total rheumatoid arthritis (RA) population defined by European League Against Rheumatism (EULAR) recommendations [Disease Activity Score based on 28 joint count (DAS28) > 3.2 and two or more failed conventional synthetic disease-modifying antirheumatic drugs (csDMARDs)]. The model first removes patients with a DAS28 ≤ 3.2 (25% of the total RA population, see Table 1 for model assumptions) from the total RA population. Next, the model subtracts the RA population with fewer than two failed csDMARDs (56.9%). This leaves 32% of the total RA population that is eligible for bDMARD treatment according to EULAR guidelines. (B) Schematic showing how the model calculates the proportion of a hypothetical country’s RA population defined by national reimbursement guidelines that specify two or more failed csDMARDs and a DAS28 > 5.1. Continuing from the EULAR-defined 32% of the total RA population (as per calculations performed in part A of this figure), the model removes DAS28 ≤ 5.1 patients (80% of the RA population, see Table 1 for model assumptions) to generate 8.5% of the total population. ⁽¹⁾ The higher disease restriction applies to national disease severity criteria that are more stringent than the EULAR recommendations of DAS28 > 3.2.