New diagnostic approach for ocular tuberculosis by ELISA using the cord factor as antigen

Background/aims-Diagnosis of ocular tuberculosis is difficult, particularly the retinal vasculitis type, because most cases occur without concurrent a ctive pulmonary tuberculosis. Recently, it has been reported that detection of antibodies against purified cord factor (trehalose-6,6'-dimycolate, TDM ), the best studied, most antigenic, and most abundant cell wall component of tubercule bacilli, is very useful for rapid serodiagnosis of pulmonary t uberculosis. In this study, an attempt was made to evaluate whether the det ection of anticord factor antibody is also useful for diagnosis of ocular t uberculosis and the necessity of antituberculous therapy for tuberculous re tinochoroiditis was discussed. Methods-Cases consisted of 15 patients with uveitis and retinal vasculitis, nine patients with presumed ocular tuberculosis, three patients with sarco idosis, and three patients with Behcet's disease. IgG antibodies against pu rified cord factor prepared from Mycobacterium tuberculosis H37Rv were dete cted by enzyme linked immunosorbent assay. Results-All cases of clinically presumed ocular tuberculosis were positive, whereas all of the cases of sarcoidosis or Behcet's disease were negative for anticord factor antibodies. When the anticord factor antibody titres we re compared on the basis of the presence or absence of previous antitubercu losis chemotherapy, the mean anticord factor antibody titre of the untreate d group showed a tendency to be higher than in the treated group, but not s ignificantly (p=0.07). Conclusions-The detection of anticord factor antibody may be useful to supp ort the diagnosis of ocular tuberculosis. Additionally, a positive result f or anticord factor antibody may indicate that tubercule bacilli are present in some organ(s) of the patient even in the absence of active systemic dis ease.