Reversal of tuberculin reaction in early tuberculosis.

The traditional concept that the tuberculin reaction when positive will remain so for the rest of the patient’s life has been widely accepted for many years. The present study was carried out to detect tuberculosis in its earliest phases by means of a positive tuberculin reaction in individuals who reacted negatively to previous test or tests. These positive patients were then followed by repeated tuberculin tests for signs of change in their reactions. The opportunity to study the natural history of tuberculosis has been provided in the tuberculosis clinics of the Los Angeles Health Departments where hundreds of tests performed weekly on contacts made it possible to select individuals whose skin reactivity changed from a negative test to a positive one. In the past two years 160 individuals have been discovered with a known negative test who have converted to a positive reaction within three months or within 12 months or were infants under one year of age who were found to have a positive reaction. It has been assumed in the case of infants under one year that they were early converters. One hundred twenty one individuals have been tested two or more times and 68 of these have changed from a positive reaction to a negative one. A total of 618 tests have been done on the entire group of 160 subjects. Although all of the subjects in order to be accepted in the study had an initial negative test or were under one year of age, the high rate of change from a positive to a negative test was very surprising. A search of the literature has revealed a few papers in which the instability or reversability of the tuberculin reaction has been found. Dahlstrom1 pointed to the finding of “calcified nodules, presumably of tuberculous origin” in individuals not reacting to tuberculin and raised the question as to whether or not this might indicate a loss of tuberculin allergy after complete healing. He showed a clear relation between the intensity of allergy and the probability of its ultimate disappearance. His data revealed that over 70 per cent of those showing the “weakest detectable reaction” (one plus) lost their allergy, and that 62 per cent of those individuals with a two plus reaction subsequently became negative. With respect to age factors, he further points out that reversability occurs in early life in an overwhelming majority and is rare in adult life. Blatman, Rapmund, Newstrand, and Alexander2 also state that “changes in tuberculin allergy have been surprising,” and they found no difference in the patients with positive as opposed to negative gastric contents in