The purpose of this study is to describe infliximab and abatacept dosing patterns (i.e., dosing amount and frequency) and costs among a population of managed care enrollees with RA. This study will also identify changes in infliximab and abatacept dosing over time and the implication these changes may have on the costs of medication administration.

This study will be conducted in two parts. The primary analysis is a longitudinal analysis, where patients' health care claims from a period during which the patient was continuously enrolled in the health plan will be used to evaluate the primary outcome (i.e., dose escalation). The second analysis will be cross-sectional, where patients' health care claims from a fixed period of time (i.e., 2008) will be used to examine health care cost.

The final enrollment for the longitudinal portion of the study was 2,001 (1,306 infliximab and 695 abatacept patients). Final enrollment for the cross-sectional portion was 3,450 (2,646 infliximab and 806 abatacept patients). There may be some overlap in these numbers.

Inclusion Criteria:

• Commercial health plan enrollees with medical and pharmacy coverage
• At least 3 claims on separate days for infliximab (HCPCS J1745) or abatacept (HCPCS C9230, J0129, J3590) administration during the subject identification period
• The 3 initial claims for abatacept occurred within a 6-week period inclusive of the index date and the three initial claims for infliximab occur within a 9-week period inclusive of the index date
• Presence of a diagnosis of RA (ICD-9-CM 714.xx)
• Continuous enrollment during the baseline and follow-up periods
• At least 18 years of age or older on the index date

Exclusion Criteria:

• Prior exposure to the index medication during the baseline period
• Diagnosis of psoriasis (ICD-9-CM 696.1), psoriatic arthritis (696.0), ankylosing spondylitis (720.0), Crohn's disease (555.x), or ulcerative colitis (556.x) in any position at any time during the study period
• Exposure to alefacept (HCPCS J0215, C9211, C9212) or efalizumab (HCPCS S0162) at any time during the study period

Commercial health plan members