Serial Interferon Gamma Release Assay in Latent Tuberculosis Infection

The aim of this report is to present results of serial interferon-gamma (IFN-[gamma]) determination (QuantiFERON-TB Gold In-Tube assay) in a 57-year-old BCG-vaccinated female health care worker with a latent tuberculosis infection. Increased IFN-[gamma], IgA, and anti-thyroglobulin (anti-Tg) autoantibodies were recorded throughout a 13-month follow-up. After 13 months the subject was clinically healthy and free from any signs and symptoms of active tuberculosis. The increased levels of anti-Tg autoantibodies may have been a concurrent process that did not impair the patient's immune status. Since false-positive IgA could be found in patients suffering from autoimmune thyroid diseases, it could be assumed increased IgA in this subject is a result of the positive interferences of goat anti-IgA antibodies. Although isoniazid prophylaxis was not used, tuberculosis did not develop during the follow-up period. Serial determination of IFN-[gamma] is necessary due to occupational exposure to tubercle bacilli.