Background The use of interferon gamma-release assays (IGRA) has become a very useful tool in the detection of latent tuberculosis (LTB) among patients on biological disease modifying anti-rheumatic drugs (bDMARDs). The IGRA offers some advantages over the intradermal tuberculin skin test (TST), such as, no requirement to re-schedule the patient for the test reading, the elimination of the inter-reader variability and higher specificity. These features facilitate the decision making when deciding which patients require tuberculosis (TB) chemoprophylaxis before starting bDMARDs, particularly in world regions with high incidence of vaccinated individuals and new TB cases. In our tertiary level hospital, the IGRA QuantiFERON-TB Test® (Cellestis Ltd, Australia), was introduced as routine screening test for LTB in late 2008 together with the usual chest X-ray, initially run concurrently and then substituting the old TST in most of the cases.
Objectives In this report, we present the benefits of its use in decreasing the number of active TB cases among rheumatoid arthritis (RA) patients prescribed bDMARDs in our centre.
Methods An audit was undertaken through the electronic medical record system of our hospital, which was implemented from January 2011 for all medical documentation. All RA patients aged 18 and over seen in the rheumatology outpatient clinic between Jan 2011 and September 2013 and on bDMARDs at any time during this period were identified. Among the cohort of RA patients on bDMARDs, we searched for patients with diagnosis of active TB or receiving anti-TB triple/quadruple therapy. Results were compared to previous RA cohort from the same hospital from the period 2003-2008, which was facilitated by two of the authors of this present paper who worked in our hospital during this period.
Results Ninety-seven individuals diagnosed with RA and treated with any of the bDMARDs available during the study period were found. There were no documented cases of TB or active TB treatment among the 97 individuals on bDMARDs during the 34-month audit period. This contrasts with the three cases of TB reactivation among the 86 patients who received bDMARDs in our centre from 2003 to 2008.
Conclusions Our data suggest that the IGRA QuantiFERON-TB Test® is more useful than the TST for the LTB screening in adult population on bDMARDs. This is particularly important in mixed populations with a high percentage of individuals being nationals from endemic countries in TB. Our recommendation is to systematically use IGRA in such settings, repeating this on an annual basis.
Disclosure of Interest None declared