The stabilization of tuberculin.

Since tuberculin may be adsorbed on to the glass surfaces with which it comes into contact, a stabilizer is added to the diluent used for preparing tuberculin dilutions. Tween 80 is widely employed for this purpose, but suffers from the disadvantage that it causes the reactions to become softer and less well-defined.The present paper describes an investigation into the possibility of replacing Tween 80 by gelatin, which is also known to be an effective stabilizer of tuberculin. In this study, groups of army recruits were each given two Mantoux tests simultaneously, one with a human or avian PPD preparation containing 0.005% Tween 80 and the other with a preparation of the same PPD (human or avian) containing 0.1% gelatin. The dilutions in each pair of tests were of the same strength.The results showed that gelatin, though eliciting firmer and larger reactions than Tween 80, was not a suitable substitute for the latter, either in the human PPD used to detect specific tuberculin sensitivity or in the avian PPD used to detect non-specific tuberculin sensitivity, since it increased the size of the reactions to a greater extent in persons with low-grade sensitivity than in those with strong sensitivity.