SPECIFICITY OF V. PIRQUET S REACTION 55 



In tuberculosis this problem is rendered still more complex by the 

 pathological anatomical findings, whereby it is shown that an extraordinary 

 high percentage of individuals have undergone tubercular infection at some 

 time during life. The clinical consideration of tuberculosis, however, does 

 not deal with the diagnosis of these harmless, practically healed tuberculous 

 foci; what the clinician desires to know is whether or not a group of symp- 

 toms manifested by a patient is of a tuberculous nature or not. In other 

 words, it is not the latent, inactive, but the active form of tuberculosis that 

 is to be diagnosed. It is that one must view the merit of the various 

 tuberculin tests from this standpoint. 



The reaction of least specificity in adults is the v. Pirquet' s cutaneous 

 reaction. In children it is far more specific. 



V. Pirquet has made the following very interesting observation.. 



Out of 747 children in Escherich's clinic in Vienna upon whom the reac- 

 tion was tried, there were: 



Clinically tuberculous 130, out of which 113 (87 %) showed a positive reaction; 

 Clinically non-tuberculous 512, out of which 104 (20 %) showed a positive reaction; 

 Doubtful 115, out of which 56 (48.6%) showed a positive reaction. 



Almost all of the tuberculous children who did not react were cachectic. 



As for the positive reaction in non- tuberculous cases, the age of the 

 child in large part explains the great differences found. 



Whereas healthy infants up to the sixth month almost never give a 

 positive reaction, healthy children of 



1 to 2 years react in 2 per cent, of cases. 



2 to 4 years react in 13 per cent, of cases. 

 4 to 6 years react in 1 7 per cent, of cases. 

 6 to 10 years react in 35 per cent, of cases. 

 10 to 14 years react in 55 per cent, of cases. 



In adults one meets with a positive v. Pirquet's reaction in more than 

 70 per cent, of all cases. V. Pirquet explains this by the presence of latent 

 tuberculosis. 



// therefore becomes self-evident, that the cutaneous reaction in adults is 

 void of any diagnostic value. A negative reaction only, can be fully relied 

 on, and that, if no cachexia exists. 



Ellerman and Erlandsen have attempted to improve upon the diagnos- 

 tic value of the cutaneous reaction by a quantitative titration of the tu- 

 berculin hypersusceptibility. They aimed to get the weakest dilution 

 which still gave a distinct cutaneous reaction. Their results showed wide 

 variations. Of those who reacted to a 1-5 per cent, tuberculin dilution the 

 great majority were clinically tuberculous; at the same time there were 

 many in whom not the faintest clinical suspicion of tuberculosis could be 

 entertained. 



