The data from a tuberculosis prevalence survey carried out in three taluks of Bangalore district in south India during 1961-68 were analysed to study (i) the prevalence of non-specific sensitivity in the community i.e., prevalence of infection with mycobacteria other than M.tuberculosis, as found by testing the population with tuberculin RT 23 of a lower strength (1 TU) and higher strength (20 TU), both with Tween 80 and (ii) additional boosting if any, resulting from testing with higher dose of tuberculin, immediately following a test with 1 TU RT 23.

The level of demarcation between infected and uninfected with 1 TU was 0-9 mm induration size and this negative group tested with 20 TU dose induration of 8 mm or more was considered positive. Prevalence of infection with M.tuberculosis in the community were 2.1% in 0-4 years, 7.9% in 5-9 years, 16.5% in 10-14 years, 33.2% in 15-24 years and overall 14.5% in 0-24 years of age group. Infection rate with other mycobacteria were 12.9%, 44.9%, 66.2%, 62.4% and 45.7% respectively in the above stated different age groups.

Testing the population with 20 TU RT 23 following a 1 TU test was found not to boost the tuberculin reactions over that observed on a single test with 1 TU only.