Evaluation of chlamydial tests in early trachoma

Abstract

An enzyme linked immunosorbent assay (ELISA) and an immunofluorescence (IF) test were compared with culture for their value in the diagnosis of chlamydial infection in early trachoma. Conjunctival swabs and scrapings from 81 school children with active trachoma from Khartoum, Sudan, were tested. Fourteen (17.3%) of the children with signs of active trachoma were positive by isolation. The sensitivities of the ELISA and IF tests, compared to cultures, were 85.0% and 68.2%, while the specificities for the ELISA and IF tests were 99.2% and 99.3%, respectively. Chlamydial IgM and IgG antibodies reactive with serotypes A-C and D-K of Chlamydia trachomatis were detected in sera of 28 (71.2%) of the 39 children from whom serum was obtained. Only eight of the 14 isolation-positive children were tested for chlamydial antibodies, and all of them had IgM and IgG antibodies at a titer of greater than or equal to 1:16. An IgG antibody titer of 1:16 or greater was detected in 20 (65.0%) of the 31 isolation-negative patients tested for chlamydial antibodies. The geometric mean titers of IgG antibodies to the antigen pools A-C and D-K were 132 and 42, respectively. Our study suggests that trachoma is prevalent in the child population studied. Clinical signs of active trachoma were found in 47.0% of the altogether 172 children investigated. ELISA can be recommended as a diagnostic tool in trachoma field surveys.