RESEARCH – November 2019

Tuberculosis in patients with rheumatoid arthritis before and after the introduction of biological treatment in Estonia: comparison of two periods

Authors: Karin Laas, Carmen Marianne Teär, Lea Pehme, Piret Viiklepp, Krista Fischer, Marika Tammaru

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Abstract

Introduction. The use of biological treatment (BT) has improved the outcome of patients with rheumatoid arthritis (RA). The sideeffects of BT include increased risk of infections and higher risk of tuberculosis (TB). Objectives. To compare TB incidence in RA patients before and after the introduction of biological treatment in Estonia; to describe TB in RA patients treated with BT.

Methods. The ID codes of patients with RA diagnoses M05 and M06.0 between 2004–2017 were obtained from the Estonian Health Insurance Fund. These ID codes were used to link with the Estonian TB register. The Estonian TB register and Statistics Estonia were used to obtain information on TB incidence among the general population. TB incidence in RA patients was calculated for the periods 2000–2007 and 2008–2016. The age and gender standardised incidence ratio of TB for RA patients was calculated. RA patients with TB were linked with the Biological Treatment Register.

Results. The number of RA patients between 2004–2017 was 5040. The one-year incidence of TB among RA patients was 24.8 per 100 000 during 2000–2007 and 30.9 per 100 000 during 2008–2016. The standardised incidence ratio of TB for RA patients compared to general population was 77% (95%UV 41–143) during 2000-2007 and 200% (95%CI 118…338) during 2008–2016. Three RA patients treated with biologicals had TB.

Conclusions. In spite of the remarkable decline in TB incidence among the general population in Estonia, the incidence of TB among RA patients had increased from 2000–2007 to 2008–2016. During 2008–2016 the incidence of TB was higher among RA patients than in the general population. The increase of TB incidence among RA patients may be connected to the introduction of biologic treatment.