A 60-year-old woman with rheumatoid arthritis, treated with methotrexate 15mg once weekly and folic acid 5mg once weekly (on a different day), complains of increasing joint pain and swelling over the past month. Examination reveals active synovitis in her MCPs and wrists bilaterally. Her DAS28 score is 5.5. According to NICE NG100, what is the most appropriate next step in her management?