[Tuberculosis contact examination and QFT-G testing for the prevention of hospital acquired infection].

Hospital acquired infection mainly occurs at hospitals, not clinics. In Japan, QFT-G is the main tool for the diagnosis of tuberculous infection among health care workers. Contact examinations are basically done for contacts of sputum smear positive TB cases, but infection may occur at fiberbronchoscopy of sputum smear negative TB cases and at the time of irrigation of TB abscess. Therefore, contact examination requires bigger target group than usual contact examinations. Mathematical model analysis of cost effectiveness examination showed that contact examinations at the age of 20s to 40s will be cost saving if it is done for the contacts with the risk of infection of 6% and beneficial for the DALY lost due to TB infection if it is done for the contacts with the risk of infection of 3%. Addition of baseline QFT for the HCWs at the age of 20s requires 100 million yen for the recovery of 1 DALY lost due to hospital acquired TB infection. Also mathematical modeling showed that periodical QFT testing of HCWs at the age of 20s to 40s will be beneficial for the DALY lost due to TB infection if the annual risk of infection will be around 2% and will be cost saving if the annual risk of infection will be around 8%. Therefore, periodical QFT is recommended for the staff working at the environment with high risk of infection (around 2% per year).