Participants and Study Cohorts

A3BC is a national registry and biobank that recruits participants into clearly defined, purpose‑specific cohorts. Cohorts are defined by disease stage, treatment status, and research intent, rather than fixed case-control groupings.

Participants may be eligible for more than one cohort over time, and may transition between cohorts as disease activity, treatment, or clinical status changes.

Participation may include registry data only, biospecimen donation, or both, according to individual consent and project requirements.

At‑Risk Cohort

Purpose

To identify predictors, mechanisms, and biomarkers associated with the onset of inflammatory arthritis or autoimmune disease in individuals at increased risk.

Eligibility

  • No confirmed diagnosis of inflammatory arthritis or autoimmune disease
  • Presence of disease‑associated risk factors, including one or more of the following:
    • Clinically suspect arthralgia (CSA) of <12 months’ duration, with:
      • MCP joint involvement, and
      • 60 minutes of morning stiffness
    • Family history of autoimmune or inflammatory rheumatic disease (e.g. first‑degree relative with rheumatoid arthritis)
    • Presence of disease‑associated autoantibodies in asymptomatic individuals (e.g. ACPA, RF)
  • Suitable for prospective follow‑up and serial biospecimen collection to capture disease transition if and when it occurs

Early Disease Cohort

Purpose

To characterise the earliest stages of inflammatory arthritis and autoimmune disease in order to inform personalised early treatment and strategies to prevent disease progression.

Eligibility

  • Symptom onset within the previous 12 months
  • Diagnosed or undifferentiated inflammatory arthritis or autoimmune disease, as defined in disease‑specific Eligibility Criteria

Starting DMARDs Cohort

Purpose

To predict initial treatment response and inform early therapeutic decision‑making.

Eligibility

  • Active inflammatory arthritis or autoimmune disease (see disease‑specific Eligibility Criteria)
  • About to:
    • Start a DMARD for the first time, or
    • Add a new DMARD to an existing treatment regimen
  • Baseline biospecimens ideally collected prior to:
    • Initiation of any new DMARD(s), and
    • Exposure to systemic glucocorticoids (IV, IM, or oral)
    • NSAIDs and simple analgesics are permitted

Switching DMARDs Cohort

Purpose

To understand mechanisms of treatment failure and to predict response to subsequent therapies.

Eligibility

  • Active inflammatory arthritis or autoimmune disease (see disease‑specific Eligibility Criteria)
  • Switching from one DMARD to another due to:
    • Inadequate efficacy
    • Intolerable adverse effects or safety concerns
    • Disease relapse or flare on the current regimen
  • Includes switching between:
    • Conventional synthetic DMARDs (csDMARDs), and/or
    • Biologic or targeted synthetic DMARDs (b/tsDMARDs)

Genetically Driven Disease Cohort

Purpose

To investigate genetic contributors to severe, atypical, or early‑onset rheumatic disease and their impact on disease course and treatment response.

Eligibility

  • High clinical suspicion of a strong genetic contribution to disease pathogenesis (see disease‑specific Eligibility Criteria)
  • Severe, unusual, or extreme disease manifestations where genetic investigation is likely to be informative
  • May include rare or monogenic‑like disease presentations where genetic studies are critical to understanding underlying mechanisms

Difficult‑to‑Treat (D2T) Disease Cohort

Purpose

To identify factors underlying difficult‑to‑treat rheumatic disease and to support studies of novel management strategies.

Eligibility

  • Diagnosis of severe, active, and difficult‑to‑control inflammatory arthritis or systemic autoimmune disease (see disease‑specific Eligibility Criteria)
  • Fulfils at least one of the EULAR criteria for difficult‑to‑treat rheumatoid arthritis:
    1. Failure of ≥2 b/tsDMARDs with different mechanisms of action after csDMARD failure (unless contraindicated), or
    2. Presence of one or more of the following:
      • At least moderate disease activity
      • Persistent signs and/or symptoms suggestive of active disease
      • Inability to taper glucocorticoids
      • Rapid radiographic progression
      • Disease‑related symptoms that significantly impair quality of life
    3. Disease management perceived as problematic by the treating rheumatologist and/or the patient
  • May also include poorly controlled systemic inflammatory disease (e.g. vasculitis, PMR, or other autoimmune conditions)

Stopping DMARDs Cohort

Purpose

To predict which participants can sustain disease control or remission after abrupt cessation of therapy.

Eligibility

  • Well‑controlled inflammatory arthritis or autoimmune disease, meeting established definitions of:
    • Remission, or
    • Low disease activity, or
    • Clinically inactive disease
      (see disease‑specific Eligibility Criteria)
  • Participant is planning abrupt discontinuation of DMARD therapy as part of routine clinical care

Tapering DMARDs Cohort

Purpose

To predict sustained disease control during and following gradual treatment reduction.

Eligibility

  • Well‑controlled inflammatory arthritis or autoimmune disease, meeting established remission or low‑activity criteria (see disease‑specific Eligibility Criteria)
  • Participant is tapering DMARD therapy as part of routine care, including tapering with intent to stop

Stable Disease Cohort

Purpose

To enable studies of stable rheumatic disease states, including baseline biology and long‑term outcomes.

Eligibility

  • Stable inflammatory arthritis or autoimmune disease, typically in remission or low disease activity
  • No planned changes to treatment regimen at the time of enrolment (see disease‑specific Eligibility Criteria)