Enhancing of tuberculin allergy by previous tuberculin test(s)
Narain, Raj; Ramanatha Rao, G.; Chandrasekhar, P. and Lal, Pyare (1966) Enhancing of tuberculin allergy by previous tuberculin test(s). Indian Journal of Tuberculosis, 13 (2). pp. 43-56.
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Enhancing of tuberculin allergy as a result of previous tests with I TU and with both 1 and 20 units has been studied by a random allocation of these tests and placebo to an un- tested and unvaccinated population of 8 villages. There was high prevalence of ‘non- specific allergy’ in the study area. It has been found that a tuberculin test does enhance the allergy elicited by a subsequent test. The enhancing effect is associated with initial allergy to tuberculin, especially that elicited by a 20 TU test, increase being almost confined to those with 10 mrn and larger reactions to 20 TU. The addition of the 20 TU test further en- hances the allergy but mostly among those with intitial reactions of 8-13 mm to the I TU. The enhancing effect increases with increase in age especially among those with 10 mm or bigger reactions to 20 TU. It is likely that the enhan- cing effect is more in communities with high prevalence of non-specific allergy. The above findings seem to be supported in the light of a much larger material. Not all persons in a group show boosting. Even among those with 10 mm and larger re- actions to 20 TU, only about 40% show an increase in allergy of 5 mm or more from their initial reactions, and are mainly responsible for Myco. tuberculosis. In such cases, when, some time later, the test is repeated an enhanced reaction of 10 or 12 mm or even a larger reac- tion, may also not be taken as evidence of infection.
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