A comparative study of tuberculin reactions to 1 TU and 2 TU of PPD - RT23

Chadha, V.K.; Jagannath, P.S.; Nagaraj, A.V.; Narayan Prasad, D. and Anantha, N. (2000) A comparative study of tuberculin reactions to 1 TU and 2 TU of PPD - RT23. Indian Journal of Tuberculosis, 47. pp. 15-20.

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Abstract

Reactions to 2 TU of PPD - RT23 with Tween 80 tuberculin were compared with those of 1TU in order to determine a suitable dose for use in tuberculin surveys. The frequency distribution of tuberculin reactionsizes to 1TU among unvaccinated children showed a bimodal distribution and a clear demarcation level for identification of the children probably infected with M.tuberculosis was observed at 17 mm. However, such a demarcation could not be observed with 2 TU dose. In addition, a significant proportion of the children with moderate reaction to 1 TU showed large reaction to 2 TU Almost all the children with unpleasant skin reactions to the2 TU dose had similar reactions to 1 TU as well. Comparison of the reaction-sizes, as read by the standard reader showed a high degree of correlation with those read by trained readers, between both the doses. The results do not support the thesis that a shiftover to 2 TU instead of 1 TU dose of PPD - RT23 for conducting tuberculin surveys would serve a useful Purpose, at least not under situations similar to the present study area.

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