The stabilizing effect of gelatin on dilutions of various tuberculins.

Adsorption of highly diluted tuberculin to the inner surface of containers is particularly pronounced for acid-precipitated PPD, and certain such preparations are routinely issued with the non-ionic detergent Tween 80 as a stabilizing agent. It has been shown, however, that Tween 80, besides its anti-adsorptive effect, also has a depressive in vivo effect, especially on tuberculin reactions that would have been weak even for a test without Tween. The authors have shown in a previous report that gelatin (0.1%) also has an anti-adsorptive effect, without apparently modifying the reaction in vivo.In the present report, the effect of gelatin on tuberculins other than acid-precipitated PPD is examined, and the loss due to surface activity in the container is found to be considerably less, though still significant, for instance, for the International Standard of PPD of Mammalian Tuberculin. The loss is particularly pronounced, and the stabilizing effect of gelatin is particularly striking, for ampoules only partly filled (i.e., with an inner surface that is large in relation to the volume of the content).It is suggested that gelatin, or some similar substance with little or no in vivo action, might be used more readily, and for more kinds of tuberculin, than Tween 80, provided that further critical studies do not reveal any so far unknown factor.