[Investigations on the equivalent of different tuberculin preparations]

Report on the comparison of the effectiveness of seven tuberculin preparations from 6 countries to RT 23. In 2 field trials performed among tuberculous patients with confirmed excretion of tubercle bacilli significant differences have been found among the preparations when their effectiveness and specificity was determined expressed in terms of the rate of negative (0-5 mm) reactions and the size of reaction and its range of variation. Only three of the seven preparations were equivalent to RT 23, one of them was even superior to it; another of the equivalent preparations originated from the stock substance of RT 23. However, one among the deviating preparations originated from RT 23, too, having a threefold higher rate of negative tuberculin reactions. Investigations in the USA with tuberculin preparations from this country done in time parallel to those reported here, had a similar result and the same conclusions. There are set limits to the comparison of testing results with tuberculins of different production. Thus, the comparison of incidence and prevalence of tuberculous infection obtained with different tuberculins must be met only with caution.