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Updated: Aug 1, 2026

The MODS method for diagnosis of tuberculosis and multidrug resistant tuberculosis
Published on: August 11, 2008
Diagnostic and clinical implications of response to tuberculin in two ethnically distinct populations from Peru and
J C Delgado1, J Quiñones-Berrocal, S Thim
1Center for Blood Research, Institute for Biomedical Research, Boston, Massachusetts 02115, USA.
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.
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