An Observational Study of Cardiovascular Risks Associated with Rheumatoid Arthritis Therapies: A Comparison of Two Analytical Approaches

Background and Objectives Comparative safety studies typically use hierarchical treatment categories that lump monotherapy and combination therapy. The consequence of this approach on study results is not clear. For example, studies of tumor necrosis factor inhibitors usually lump users regardless of whether they are using the drug alone or in combination with other agents. This study explored the importance of lumping vs splitting users of monotherapy and combination therapy. We also explored whether the timing of disenrollment from Health Plan membership was informative as an outcome variable when interpreting unmeasured, time-varying confounding.