Increased detection of latent tuberculosis by tuberculin skin test and booster phenomenon in early rheumatoid arthritis patients

The incidence of tuberculosis (TB) in rheumatoid arthritis (RA) patients is up to four times higher when compared to the general population, but their risk increases with the use of TNF-a drugs. Appropriate screening of latent tuberculosis infection (LTBI) and proper management of such cases substantially reduce the incidence of active TB. Tuberculin skin test (TST) is a widely used method for the detection of LTBI. The time of diagnosis of RA as well as the age of the patient might modify the TST performance. We did an observational, comparative study of RA patients with early and established disease, with the objective to know the prevalence of LTBI using the TST and booster test; an induration ≥5 mm was considered reactive. We evaluated 143 patients (83 [58 %] early RA patients). We found 31.3 and 21.7 % TST positivity in early and established RA patients, respectively. With the use of booster test, the positivity increased to 46.5 and 28.8 %, respectively (p = 0.048, OR 1.33, 95 % CI 1.01–1.75). In conclusion, we found that TST and booster test increased LTBI detection in early RA patients, which may suggest that time of RA diagnosis might affect cellular immunity and therefore the TST response.