Fig. 1

Study design. Abbreviations. RA: rheumatoid arthritis; DMARD: disease-modifying anti-rheumatic drug; bDMARD: biological DMARD; tsDMARD: targeted synthetic DMARD; D2T-RA: difficult-to-treat; e-D2T-RA: episodic D2T-RA; p-D2T-RA: persistent D2T-RA