A COMPARISON IN THE UNITED STATES OF AMERICA OF TWO TUBERCULINS, PPD-S AND RT 23.

A comparison of PPD-S and RT 23 was carried out in three pairs of population groups. Tuberculin sensitivity was thought to have resulted, in one of each pair, almost entirely from infection with Mycobacterium tuberculosis, and in the other, from the diverse causes operating in the United States of America. Among persons with specific tuberculin sensitivity, 2.5 TU of RT 23 in a saline buffer containing Tween 80 were approximately equivalent to 5 TU of PPD-S in phosphate-buffered saline diluent. Among persons whose sensitivity appeared to have resulted from infections with organisms antigenically similar to the Battery strain of unclassified mycobacteria, 2.5 TU of RT 23 in Tween 80 gave considerably more reactions than 5 TU of PPD-S.