Practical Application of a Hemagglutination Reaction in Tuberculosis.

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Abstract
Serological methods have been unsatisfactory in the diagnosis of tuberculosis. Difficulties may have arisen from the lack of a suitable antigen of known chemical composition which was capable of reacting with its corresponding antibody. These difficulties were for the most part obviated in 1948 when Middlebrook and Dubos (Jour. Exptl. Med. 88: 521.1948) described a specific hemagglutination reaction between sheep erythrocytes treated with a water-soluble fraction (rich in poly-saccharide) of mammalian tubercle bacilli and the sera of tuberculous patients. Because of the difficulty in preparing large quantities of the polysaccharide antigen, it became desirable to find a more easily available supply of antigenic material. A concd. prepn. of old tuberculin (Lederle), diluted 1-12 in physiol. saline at pH 7, was found to be suitable for sensitizing sheep erythrocytes for this test. Heterologous reactions were noted in about 6-8% of sera from non-tuberculous patients or normal adults, but these reactions were of low titer. Because of the cross reactions, it appears probable that only titers of 1:8 or higher are indicative of tuberculous infection. The sera of 216 normal adults and patients with syphilis or non-tuberculous chest diseases were tested for tuberculous antibodies by the hemagglutination reaction: 12 had positive reactions in serum dilution of 1:2, and one in dilution of 1:4. The sera of 168 patients with active tuberculosis showed 92% positive reactions in dilutions ranging from 1:8 to 1:512. Sera from 33 apparently cured tuberculous individuals revealed no reactions in 31, and positive reactions in 2 in a serum dilution of 1:2. This test apparently not only provides a valuable diagnostic tool, but,unlike the tuberculin skin test, appears to indicate the presence of tuberculous activity.