Epidemiology and Treatment of New-Onset and Established Rheumatoid Arthritis in an Insured US Population

To investigate the epidemiology and treatment of rheumatoid arthritis (RA) in a population broadly representative of employed adults in the US, using a retrospective cohort design.

Incident and prevalent RA cohorts were defined from a sample of 4.66 million adults with complete followup data from the period of January 2005 through September 2008 in the Pharmetrics medical claims database. Demographics, comorbidity, and medical therapies were summarized using descriptive statistics.

Median duration in the database was 5.7 years. Age- and sex-adjusted incidence in 2006 was 0.71 per 1,000 persons at risk (n = 3,992) and prevalence in 2005 was 0.63% (n = 30,530). Within 12 months after diagnosis, 65%, 64%, and 20% of the incident cohort had been prescribed corticosteroids, nonbiologic disease-modifying antirheumatic drugs (DMARDs), and tumor necrosis factor (TNF) inhibitors, respectively. Median time to first anti-TNF prescription was 6 months; 31% switched to a second drug and 15% to a third. An aggressive subcohort (11% of incident patients) received more DMARDs (83%) and TNF inhibitors (43%), and was more likely to switch. Twenty-eight percent of incident patients received only symptomatic therapy over a minimum of 1.75 years of followup; these patients were older with more comorbidities and contraindications to methotrexate.

In this insured population-based cohort, only two-thirds of newly diagnosed RA patients were prescribed a DMARD in year 1 and 28% received no antirheumatic therapy. Although limited by lack of clinical information and by left-censoring, administrative databases capture clinical practice and suggest that gaps exist in treatment options available to a significant number of patients.