Sensitivity to mycobacterial antigens

In a study carried out in 1971, each of 3 030 persons was tested simultaneously with tuberculin RT 23 and two other PPD sensitins-PPD-S and PPD-A, PPD-B and PPD-Y, or PPD-G and PPD-F. Of the 2 558 persons whose reactions were read, 20.2% had previously been vaccinated with BCG and 79.8% were unvaccinated. RT 23 and PPD-S produced almost identical mean indurations. Both elicited much higher reactions than the sensitins prepared from atypical mycobacteria. Correlation of the sizes of induration obtained with RT 23 and with the other sensitins showed that low-grade sensitivity was due to cross-reactions to human tuberculous infection and that in no case did an "atypical" sensitin produce an induration of wider diameter than RT 23 did. It is concluded that nonspecific tuberculin sensitivity was not demonstrated in this study.