Objectives:

To elucidate the effects of achieving sustained simple disease activity index (SDAI) remission in the progression of joint space outcomes using high-resolution peripheral quantitative CT (HR-pQCT) in patients with early rheumatoid arthritis (ERA), and what the independent effects of erosion /JSW progression are on patient's function.

Hypothesis to be tested: Effective control of inflammation in ERA patients who can achieve sustained SDAI remission will have less progression of joint damage then patients who cannot achieve sustained SDAI remission.

Design and subjects: 110 consecutive ERA patients will participate in this 1-year prospective, hospital-based, cohort study.

Study instruments Metacarpophalangeal joints 2-4 will be measured using HR-pQCT Interventions All participants will receive 1-year tight-control treatment according to a standardized protocol aiming at SDAI remission. Physical function will be assessed by Health Assessment Questionnaire (HAQ) at each visit. HR-pQCT and radiographs will be performed at baseline, 6 (HR-pQCT only) and 12 months. Quantitative analysis of joint space width (JSW) and volume, erosion number and volume, and marginal osteosclerosis (bone apposition at the base of the erosion) will be evaluated by HR-pQCT. Radiographic progression will be scored using van der Heijde-Sharp (SvdH) score.

Outcome measures: The primary outcome is the change in JSW and volume over a period of 12 months. Main secondary outcomes include changes in the i) number and size of erosion, ii) SvdH score and iii) HAQ over a period of 12 months.

Expected results: Patients who can achieve sustained SDAI remission will have less joint damage and functional loss compared

Inclusion Criteria:

• fulfilled the 2010 ACR/EULAR classification criteria for RA
• have symptoms onset of less than 2 years,
• have active disease (SDAI >3.3)

Exclusion Criteria:

• have severe clinical deformity at the 2nd, 3rd or 4th MCP joint which precluded a reliable HR-pQCT examination and resulted in motion artefacts influencing the scanning accuracy
• are pregnant or breast feeding

Starting from July 2020, all new cases referrals to the rheumatology clinic of the Prince of Wales Hospital (PWH) and four other regional hospitals in Hong Kong will be screened by a research assistant. Patients referred as RA, possible RA or undifferentiated arthritis will be contacted through telephone. Patients with at least 1 tender and swollen joint and with duration of symptoms less than 2 years and with no previous use of DMARDs will be invited to a screening visit at the early arthritis clinic of the PWH within 2 weeks of the referral, where they will be formally assessed by a rheumatologist.