TUBERCULIN REACTION 631 



definite pulmonary lesion is tuberculous, a focal reaction, on the other 

 hand, tells definitely of the presence of the disease, and shows, in some 

 measure at least, its extent. In these questionable cases, therefore, the 

 subcutaneous injection of tuberculin finds its most important applica- 

 tion, since a definite focal is of more value than a local reaction. 



Tuberculin may also be of service when the symptoms suggest the 

 presence of a pulmonary tuberculous lesion, but the physical signs are 

 indefinite. Here the focal reaction is likely to be slight and to escape 

 detection, so that one .of the cutaneous tests are usually employed. 



2. In the diagnosis of bone, joint, and glandular tuberculosis the sub- 

 cutaneous test is likely to be most valuable, on account of the focal reac- 

 tion of hyperemia, swelling, heat, and pain about the lesions. The 

 cutaneous test is also valuable, but since this may react on account of 

 the presence of a lesion situated elsewhere, the focal reaction is more 

 conclusive. According to Hamman and Wolman, (a) a focal reaction 

 confirms the diagnosis of tuberculous bone or joint disease; (b) an ab- 

 sence of reaction to the subcutaneous test excludes, with the highest 

 probability, the presence of tuberculosis. 



3. In the diagnosis of genito-urinary and pelvic tuberculosis a positive 

 tuberculin reaction is of little value unless the subcutaneous method is 

 employed and the physician is sure of his ability to detect a focal reac- 

 tion, a proceeding that may be very difficult or indeed impossible. A 

 positive cutaneous test indicates the presence of a lesion somewhere 

 in the body, without disclosing the nature of the renal or pelvic lesion. 

 A negative reaction, however, is of more value, especially when the 

 physician bears in mind the conditions under which a falsely negative 

 result may occur. 



4. In the diagnosis of tuberculosis of the eye, ear, and larynx, the tu- 

 berculin reaction usually has a limited value, because the nature of the 

 disease can be so readily detected by direct inspection. In tuberculosis 

 of the larynx a focal reaction may be dangerous on account of edema. 

 Similarly in advanced tuberculosis of the ear a focal reaction may lead 

 to extension of the process to the meninges. In these instances, there- 

 fore, a cutaneous test should first be made, and if it is found to be nega- 

 tive or inconclusive, the subcutaneous test should be applied with extra 

 caution. 



5. In the diagnosis of tuberculosis of the skin tuberculin may occasion- 

 ally prove of value especially the focal reaction following subcutaneous 

 injection or a direct local application upon the lesion with a weak dilu- 

 tion, such as a 1 per cent, solution of old tuberculin. 



