ATLANTA – Rheumatoid arthritis patients who switch from one tumor necrosis factor inhibitor to another during the course of their disease are not at increased risk for serious infections, according to an analysis of data from a large health claims database.
The unadjusted rates of first serious infection in 13,752 RA patients who received only one tumor necrosis factor (TNF) inhibitor between Jan. 1, 2001, and Dec. 21, 2007, and in 2,293 RA patients who switched at least once from one TNF inhibitor to another during that time period did not differ significantly in either a model that analyzed infection rates within 90 days of any health insurance claim for a TNF inhibitor (the index date), or in a model that analyzed infection rates at any time after the index date, Bao-Anh Nguyen-Khoa, D.Pharm, reported at the annual meeting of the American College of Rheumatology.
Rates of first serious infection in the 90-day model were 6.31 and 6.78/100 patient-years in the nonswitchers and switchers; rates in the ever-treated model were 8.45 and. 9.10/100 patient-years in the nonswitchers and switchers, he said.
Rates of first serious infection in both models declined significantly from the first year after the index date, to the second year after the index date and beyond. In the 90-day model, those rates declined from 8.59 to 2.66/100 patient-years in the nonswitchers, and from 8.72 to 2.64/100 patient-years in the switchers. In the ever-treated model, the rates declined from 10.15 to 4.18/100 patient-years in the nonswitchers, and from 10.11 to 4.44/100 patient-years in the switchers, said Dr. Nguyen-Khoa, a pharmacoepidemiology consultant in Arlington, Va.
After adjustment for age, sex, selected comorbidities, Charlson comorbidity score, hospitalizations, and other RA treatments, there still was no significant difference between the nonswitchers and switchers in the risk of serious infection for either attribution model (hazard ratio, 0.93 in the 90-day model, and hazard ratio, 0.94 in the ever-treated model).
Patients in the health insurance claims database used for this study were included if they had not been treated with other biologic agents, and if baseline data were available for at least 365 days of enrollment prior to the index date. Serious infections were defined as infections requiring intravenous antibiotic treatment or hospitalization.
Several prior studies have documented an increased risk of serious infections in patients using TNF inhibitors, with incident rates ranging from 3.6 to 10.5 cases per 100 patient-years, and with similar findings to the current study in regard to differences in infection rates in the first year compared with the second year. However, although switching anti-TNF agents is a common strategy in RA patients who experience adverse events or lack of efficacy, infection rates in patients who switch drugs have not been widely studied, Dr. Nguyen-Khoa said.
In the current study, he and his colleagues demonstrated that switching TNF inhibitors does not increase risk, and they also reported a reduced rate of serious infections in patients who survived into the second year – a finding that corresponded with the results of those earlier studies, he said.
This study was supported by Genentech and Biogen IDEC Inc. Dr. Nguyen-Khoa said he had no conflicts of interest.