Good concordance between two batches of new tuberculin in the Mantoux test

Two batches of new tuberculin prepared from different unheated cultures of M. tuberculosis, 8 years apart, were tested for concordant skin reactions in the WHO standard Mantoux test. Both batches T1327 and T1456 were simultaneously injected (0.1 ml) into the dorsal aspects of the forearms of 123 school children, aged 11-13 years, who had been BCG vaccinated at birth. The mean size of the induration to T1327 was 10.3 (SD 4.4) mm and to T1456 it was 11.3 (SD 4.2) mm. There was a significant linear correlation between the indurations caused by both batches (r = 0.91, P < 0.0001). The discrepancies between the readings were all within the limits of a 5 mm category. The mean size of the BCG scar was 8.1 (SD 4.8) mm, and there was a trend associating smaller BCG scars with smaller tuberculin responses which did not reach statistical significance. The two different batches of new tuberculin gave remarkably concordant results in WHO standard Mantoux testing illustrating the stability of the production process and suggesting that the results obtained in studies using different batches of new tuberculin are comparable.