Abstract
Interferon Gamma Release Assay (IGRA) is an indispensable method for diagnosing tuberculosis infection because of its excellent specificity and sensitivity owing to M. tuberculosis specific antigens. There seems to be no significant difference in sensitivity or specificity between QuantiFERON Gold In-tube and T–SPOT TB, both of which are available in Japan. Results of IGRA wane after a certain time from infection or fluctuate if it is repeated. Therefore, careful consideration is required for interpretation. For infection control in medical facilities, IGRA at the start of employment is recommended to get baseline datum, however, LTBI treatment for a positive reactor is unnecessary, if recent infection is not probable. For contact examination, the examinee should be decided depending on infectiousness and infectious period of the index case, closeness of contact, and individual risk for developing active disease. Timing of IGRA is basically two to three months after the final contact. However, modification should be considered depending on the situation. It is significant for hospital infection control to give LTBI treatment for immune-depressed patients with high risk for developing tuberculosis. Careful consideration for influence of the immune-depressed condition is required to interpret the data.
