Drug Concentration, Immunogenicity, and Efficacy Study in Patients With Rheumatoid Arthritis Currently Treated With Etanercept, Adalimumab, or Infliximab

cross-sectional Population will be selected through convenience sampling. Patients
sequentially visiting the rheumatology clinic for routine care who are receiving etanercept,
adalimumab, or infliximab for between 6 and 24 months will be evaluated for eligibility and
interest in participation. A maximum of 200 patients per treatment will be enrolled.

Inclusion Criteria:

1. Age 18 years or older.

2. Diagnosis of RA based on the 1987 American College of Rheumatology revised criteria

3. Current continuous treatment with either etanercept, adalimumab, or infliximab for a
minimum of 6 months and maximum of 24 months.

Exclusion Criteria:

1. Treatment with biosimilar or investigational etanercept, adalimumab, or infliximab
within past 6 months.

2. Treatment with any other investigational drugs within past 3 months or five half
lives of the drug, whichever is longer.

3. Any medical condition that would interfere with rheumatoid arthritis evaluation or
other study assessments (eg, fibromyalgia, lupus).