[Diagnostic value of various tuberculin preparations]

Abstract

Despite declining incidence of tuberculosis in developed countries importance of tuberculin testing has not subsided. Previous investigations of the equivalence of 7 tuberculin preparations from 6 countries to RT 23 have shown differences in the diagnostic value of the tuberculin preparations. The smallest rates of negative skin-reactions in cases with bacteriologically confirmed tuberculosis were found with the hungarian tuberculin PPD-5 TU (HU 5 TU) and RT 23. The national tuberculin PPD Dessau 2 TU showed highest rates of non-reactors in tuberculous patients. In 400 cases of active bacteriologically confirmed tuberculosis further investigations were carried out to compare biologic equivalence of RT 23, HU 5 TU, tuberculin PPD Dessau 2 TU and the test-preparation PPD Dessau 5 TU with and without Tween addition and 7.5 TU without Tween. The results showed that with increase of antigen concentration to 5 TE or 7.5 TU the smaller reactions of 6 to 10 mm could be strengthened with a small, statistically not significant, increase of the mean value of reaction size but no increase of larger reactions of more than 20 mm. The rate of false negative reactions decreased using the test-preparation PPD 7.5 TU. The results allow to recommend the production of a national tuberculin preparation with higher antigen concentration biologically equivalent to RT 23 or HU 5 TU.