

TUBERCULIN REACTION 589 



Carpenter, and Cope, 1 the various tuberculin reactions are likely to 

 yield results that are quite similar. 



The Value of Tuberculin in Diagnosis. As previously stated, a reac- 

 tion to tuberculin means essentially that the individual reacting has a tu- 

 berculous infection, and in itself means nothing more. Since tuberculin 

 tests disclose inactive and relatively benign tuberculous infections, it 

 has little value, in doubtful cases, in aiding us to decide whether or not 

 the individual has active disease, which clinically is the type of infection 

 about which we are most concerned. Lack of critical discernment in 

 the interpretation of the reaction and its apparent indefiniteness have 

 contributed toward diminishing its diagnostic value. 



A positive tuberculin reaction is to be regarded as a symptom, or as 

 another link in the chain of clinical evidence, but is not in itself indisputable 

 evidence that a certain lesion is tuberculous, for it can never decide with 

 certainty an otherwise doubtful diagnosis. A similar example is that of 

 a positive Wassermann reaction in a patient with a lesion in the throat; 

 such a reaction does not necessarily mean that the lesion is syphilitic, 

 for the lesion itself may be cancerous, although, coincidentally, a latent 

 syphilitic infection may be present. 



If tuberculin could differentiate between active and inactive lesions 

 according to the degree of reaction, its value would be greatly increased. 

 While the studies of Krompecker and Romer upon animals indicate that 

 the more virulent the infection the greater the degree of hypersensitive- 

 ness, no such fixed relation exists in man. All that may be said is that, 

 in general, the severer the reaction, the more acute the infection. On 

 the other hand, acute miliary tuberculosis or chronic cachectic cases 

 may react negatively. 



The conditions under which a negative reaction may be obtained in a 

 tuberculous person are to be carefully borne in mind, for if these can be 

 excluded, . a negative tuberculin reaction precludes, in all probability, an 

 active or clinically important tuberculous lesion. Tuberculin has, there- 

 fore, a higher negative than a positive value in diagnosis. 



While it is obviously beyond the scope of this volume to discuss the 

 diagnostic value of tuberculin in tuberculous infection of the different 

 organs, I may briefly refer to a few of the more important conclusions 

 reached by individual investigators of large experience in this particular 

 field: 



1. In the diagnosis of pulmonary tuberculosis, while a positive consti- 

 tutional or local tuberculin reaction is never conclusive evidence that a 

 1 Archiv. Int. Medicine, 1908, ii, 405. 



