RESUMO
BACKGROUND: The QuantiFERON-TB Gold assay and tuberculin skin test (TST) have been useful test for diagnosing latent tuberculosis infections (LTBI). However, there are few reports on the efficacy of the QuantiFERON-TB Gold assay and TST in evaluating the response after the treatment of LTBI. This study examined the changes in the TST and QuantiFERON-TB Gold assay before and after a treatment for latent tuberculosis in health care workers (HCWs) at a local tertiary hospital. METHODS: A cohort of volunteers working as nurses and doctors who underwent a TST and QuantiFERON-TB Gold assay was established. The volunteers positive for the QuantiFERON-TB Gold assay had been treated with 3 months of isoniazid (INH) and rifampin (RFP). After completing treatment, the TST and QuantiFERON-TB Gold assay were repeated. RESULTS: Of the 48 participants (14 doctors, 34 nurses, M: F=11:37, mean age=29.9+/-5.5 years, mean employment period=74.9+/-64.3 months), 19 (39.6%) tested positive to the TST (mean induration=19.1+/-9.7 mm) and 8 (16.7%) were QuantiFERON-TB Gold assay. Among them, one had active pulmonary tuberculosis. Seven volunteers were consistently positive to both the TST and QuantiFERON-TB Gold assay after being medicated with INH and RFP for 3 months. CONCLUSION: TST and QuantiFERON-TB Gold assay are unsuitable for evaluating the treatment response of LTBI because they were consistently positive both before and after the anti-tuberculosis medication.