According to the Centers for Disease Control and Prevention, the 1999 and 2000 incidence rates for tuberculosis (TB) in the US population were 6.4 and 5.8, respectively, per 100,000 persons. Recently, reports of TB following infliximab administration have raised questions regarding the rate of TB in patients with rheumatoid arthritis (RA) generally and in those treated with infliximab in clinical practice. We undertook this study to determine the baseline rate of TB in RA prior to the introduction of infliximab and to determine the rate of TB among those currently receiving infliximab.
We surveyed patients with questionnaires, followed by detailed validation from medical records and physician reports. In study 1, we evaluated 10,782 RA patients in 1998-1999 prior to the widespread use of infliximab. In study 2, we evaluated 6,460 infliximab-treated patients in 2000-2002.
In study 1, the lifetime rate of TB was 696 per 100,000 patients (95% confidence interval [95% CI] 547-872). Of these cases, 76.8% occurred prior to the onset of RA. During the period of prospective followup, 1 case of TB developed during 16,173 patient-years of followup, yielding a rate of 6.2 cases (95% CI 1.6-34.4) per 100,000 patients. In study 2, the TB incidence rate among infliximab-treated patients was 52.5 cases (95% CI 14.3-134.4) per 100,000 patient-years of exposure. Three of the 4 cases occurred in patients with a history of TB exposure, and no cases occurred in persons with recent TB skin tests or prophylaxis.
The rate of TB is not increased in RA patients generally. Among infliximab-treated patients, the rate is 52.5 cases (95% CI 14.3-134.4) per 100,000 patient-years of exposure. A thorough medical history regarding TB, as well as tuberculin testing and radiographic examination (if indicated), should be an essential component of anti-tumor necrosis factor therapy.