CRP and rheumatoid arthritis: RA: rheumatoid arthritis; N/L group: no/low US inflammation; M/H group:  moderate/high US inflammation; PGA: patient global assessment; TJC: tender joint count; SJC: swollen joint count; HAQ: health assessment questionnaire; US: ultrasonography; MTX: methotrexate; DMARD: Disease modifying anti rheumatic drug; PSL: prednisolone; NSAIDs: non-steroidal anti-inflammatory drugs; CRP: C-reactive protein; ESR: erythrocyte sedimentation rate; ACPA: anti-cyclic citrullinated peptide antibody; RF: rheumatoid factor