Trial of a self-firing heaf multiple puncture machine

Abstract

A new type of multiple puncture tuberculin testing machine, which is operated by a predetermined pressure being applied to the end plate was designed to reduce the effects of variation in testing technique. A trial comparing the new and standard Heaf multiple puncture machines is described. This confirmed that the Heaf multiple puncture test, whether done with the new or with the standard machine, can consistently classify subjects as positive and negative. The results obtained with the standard multiple puncture machine showed that the effect of the tester on the size of the reaction had persisted for two years. The trial also showed that the pressure of the end plate on the skin at the moment of release had a decided effect with one tester on the size of the resulting reaction. The self-firing machine did not eliminate differences between testers in the size of reactions produced. It did limit the number of small reactions. The self-firing multiple puncture machine is therefore thought to offer greater safeguards against tester error, but further study of the mechanics of the multiple puncture technique is needed.