Observations Upon the Specificity of the Complement Fixation Test for Lymphogranuloma Venereum

The Lygranum complement-fixation test affords valuable diagnostic information when sera are titrated, particularly in dilutions of 1:20 and 1:40. Titers of 1:40 and above offer good evidence of infection with the agent of lymphogranuloma venereum. Titers below 1:20 can only be interpreted following examinations of subsequent specimens of serum, employing quantitative procedures. Titers of 1:40 or above were obtained with sera from 56 per cent of patients from a clinic for anogenital lesions and from 97 per cent of patients with a clinical diagnosis of lymphogranuloma venereum. If sera are tested only in dilutions of 1:5 the Lygranum complement-fixation test has limited usefulness. Under such conditions non-specific reactions may occur in apparently healthy individuals, in upper respiratory infections, as well as in the presence of venereal diseases other than lymphogranuloma venereum. While early syphilis may occasionally produce false positive reactions with the Lygranum C. F. antigen, these reactions can usually be screened out by titration studies, in which the 1:40 dilution is considered as the critical titer for diagnosis, or by the more tedious procedure of absorption of sera with Kahn antigen. Our experience has been that when titers of 1:40 or higher are manifested in the Lygranum C. F. test, absorption with Kahn antigen does not remove the reactivity for the Lygranum C. F. antigen, thus providing undisputable evidence that multiple infection is present.