Comparison of the tuberculin skin test and interferon gamma release assay for the screening of tuberculosis in adolescents in close contact with tuberculosis TB patients.

BACKGROUND: The tuberculin skin test (TST) frequently yields false positive results among BCG-vaccinated persons thereby limiting its diagnostic value particularly in settings with high BCG vaccination rate. We determined the agreement between IGRA and TST using 2 cutoff values and identified possible relationships between the results of these tests and the development of active tuberculosis. METHODOLOGY: Adolescents aged 11-19 years in close contact with smear-positive tuberculosis cases and with normal chest radiographs were recruited from middle and high schools in South Korea. The TST was conducted by trained nurses, and blood was drawn for the QuantiFERON-TB Gold In-Tube (QFT-GIT). Participants were followed up for 2 years to check for incidence tuberculosis. RESULTS: A total of 2,982 subjects were included in the study, the average age was 15.1 years (SD 1.3), 61% had BCG vaccination scars. The agreement of QFT-GIT and the TST was low (κ = 0.38, 95% CI 0.32 to 0.42) using 10 mm cutoff; however, when the 15 mm cutoff was used, the agreement was intermediate (κ = 0.56, 95% CI 0.50 to 0.61). The odds ratio (OR) for the development of active tuberculosis was 7.9 (95% CI 3.46 to 18.06) for QFT-GIT positive patients, 7.96 (95% CI 3.14-20.22) for TST/QFT-GIT+ and the OR 4.62 (95% CI 2.02 to 10.58) and 16.35 (95% CI 7.09 to 37.71) for TST 10 mm and 15 mm cutoff respectively. CONCLUSIONS: The results of this study suggest that the TST cutoff point for patients aged 11-17 years would be 15 mm in other study. The OR of QFT-GIT for the development of active tuberculosis and its intermediate agreement with TST using 15 mm cutoff demonstrates its role as an adjunct diagnostic tool to current clinical practice. Positive responders to both TST and QFT-GIT at the outset may benefit from chemoprophylaxis.

The Current Status of BCG Vaccination in Young Children in South Korea.

BACKGROUND: Delivery of Bacille Calmette-Guréin (BCG) Tokyo vaccine, with the multipuncture device, has been much preferred over BCG Pasteur, with the intradermal method, possibly due to the easier manner of administration, a desire to avoid any trouble with scars, as well as side effects and higher profits to providers in South Korea. METHODS: To determine BCG scar status in 0~6 year old children vaccinated with two BCG vaccines (Pasteur BCG vaccine with intradermal method and BCG Tokyo vaccine with percutaneous method), the data from the national BCG scar survey in 2006 was analyzed. RESULTS: Based on the national survey, the high proportion that were vaccinated with BCG Tokyo vaccines with the multipuncture method (64.5%) was noted in 0~6 year old Korean children. From inspection of scar formation, as an indicator of vaccination, the median number of the visible pin scars from the percutaneous method was 16 (interquartile range, 12~18) in the Korean children, and pin scars decreased as the age of the children increased (p<0.001). CONCLUSION: The findings in this survey clearly showed a growing preference of parents for the BCG Tokyo vaccines by the multipuncture method in South Korea.