BACKGROUND: Proper interpretation of the tuberculin skin test (TST) requires knowledge about prior vaccination with BCG and the results of epidemiological studies with the test. DESIGN: A TST survey was performed in patients with pulmonary tuberculosis (PTB) in two ethnically distinct populations from Cambodia and the Peruvian Andes. We examined interferon-gamma (IFN-gamma) production in whole blood cultures stimulated by ESAT-6, a Mycobacterium tuberculosis specific antigen in tuberculin-positive BCG-vaccinated Peruvians with no history of PTB. RESULTS: Of the 81 Peruvian PTB patients tested, none had a skin response to tuberculin that was <10 mm, whereas 98 of 364 Cambodian PTB patients (37%) did. Furthermore, TST skin reaction sizes were significantly larger in Peruvian (21.69+/-5.46 mm) than Cambodian patients (11.42+/-7.74 mm; P < 0.0001). IFN-gamma production in response to ESAT-6 correlated with a TST reaction size >15 mm indicating previous infection with M. tuberculosis (kappa coefficient of agreement 0.66; 95%CI 0.29-1). CONCLUSION: Ethnicity is an important factor in the interpretation of TST results in both BCG-vaccinated and non-vaccinated individuals. A negative TST appears to be a useful indicator to rule out tuberculosis infection in Peruvians of Quechua origin.
BACKGROUND: Proper interpretation of the tuberculin skin test (TST) requires knowledge about prior vaccination with BCG and the results of epidemiological studies with the test. DESIGN: A TST survey was performed in patients with pulmonary tuberculosis (PTB) in two ethnically distinct populations from Cambodia and the Peruvian Andes. We examined interferon-gamma (IFN-gamma) production in whole blood cultures stimulated by ESAT-6, a Mycobacterium tuberculosis specific antigen in tuberculin-positive BCG-vaccinated Peruvians with no history of PTB. RESULTS: Of the 81 Peruvian PTB patients tested, none had a skin response to tuberculin that was <10 mm, whereas 98 of 364 Cambodian PTB patients (37%) did. Furthermore, TST skin reaction sizes were significantly larger in Peruvian (21.69+/-5.46 mm) than Cambodian patients (11.42+/-7.74 mm; P < 0.0001). IFN-gamma production in response to ESAT-6 correlated with a TST reaction size >15 mm indicating previous infection with M. tuberculosis (kappa coefficient of agreement 0.66; 95%CI 0.29-1). CONCLUSION: Ethnicity is an important factor in the interpretation of TST results in both BCG-vaccinated and non-vaccinated individuals. A negative TST appears to be a useful indicator to rule out tuberculosis infection in Peruvians of Quechua origin.
Authors: Victoria Ward; Branwen J Hennig; Kouzo Hirai; Hideki Tahara; Akihiro Tamori; Ritu Dawes; Mineki Saito; Charles Bangham; Henry Stephens; Anne E Goldfeld; Warunee Kunachiwa; Nipapan Leetrakool; Julian Hopkin; Sarah Dunstan; Adrian Hill; Walter Bodmer; Peter C L Beverley; Elma Z Tchilian Journal: Immunogenetics Date: 2006-03-15 Impact factor: 2.846