Gelatin and Tween 80 as stabilizing agents for tuberculin dilutions

The addition of Tween 80 to tuberculin dilutions as a stabilizer is known to increase the size of moderate and strong reactions but to reduce that of weak reactions. In order to find out whether this effect on reaction size is connected with the stabilizing action, a study was carried out to compare the reactions to tuberculin plus Tween 80 with those to tuberculin plus gelatin, an almost equally effective stabilizer. In this study, 2519 young adults were given simultaneously, by random selection, one of four experimental tests (1 TU of RT 23 with gelatin, 2 TU of RT 23 with gelatin, 2 TU of RT 23 with Tween 80 and 2 TU of RT 23 without stabilizer) in one arm and a reference test (2 TU of RT 23 with Tween 80) in the other arm.The results showed very clearly that gelatin, unlike Tween 80, increased the size of the weak, moderate and strong reactions uniformly, and it is therefore concluded that the depressive effect of Tween 80 on weak reactions is not directly connected with the stabilizing action, but is an additional effect.