STUDY OF THE DOUBLE-DIFFUSION GEL PRECIPITATION TEST IN TUBERCULOUS PATIENTS - WITH SPECIAL REFERENCE TO TECHNICAL PROBLEMS

Abstract

The double-diffusion gel precipitin test for the antibodies to Mycobacterium tuberculosis possesses a high degree of sensitivity provided the full effectiveness of the test is exploited by the use of multiple antigens in serial dilution. A satisfactory method of standardizing antigen has not been found. Consequently, to avoid false negative reactions, it seems necessary to check these against more than one batch of antigen and to employ the antigen in serial dilution. The test can hardly be considered a quantitative one and the sensitivity is such that it furnishes little information about the extent or activity of the disease. Moreover, the immune response that results from continuous exposure to tuberculosis can be of the same degree as that which results from active disease. This study provides no precise information regarding the disappearance of antibody after arrest or complete healing beyond the fact that negative reactions do occur in former tuberculous patients with noninfectious sputum. The healthy tuberculin-positive person can be expected to react negatively to the gel diffusion test. It follows that a positive test means active disease except in the special situation already noted, namely, long continuous exposure to tuberculosis. Experience up to the present time-and this is only preliminary-indicates that when interpreted with circumspection the gel diffusion test can be of critical value in distinguishing tuberculosis from nontuberculous disease.