Laboratory study of trachoma in Egyptian rural schoolchildren.

Cytological preparations from the conjunctiva of schoolchildren were examined by Giemsa staining and by an indirect fluorescent antibody (FA) technique. In addition, chlamydial group-specific antibodies in sera were measured with the complement fixation (CF) test. It has consistently been shown that the FA technique is more sensitive than Giemsa staining for the cytological demonstration of intracytoplasmic inclusions in conjunctival cells from trachoma patients, but reports differ regarding the degree of its superiority. The present study confirmed that the FA technique is more sensitive. Furthermore, the demonstration of intracytoplasmic inclusions by the FA technique correlated to a high degree with the intensity of the clinical signs of trachoma. With chlamydial (bedsonial) group antigen, the CF test yielded positive results in only a small proportion of cases. However, in areas where the disease is hyperendemic, a standardized CF test may show a correlation of positive results with the intensity of clinical signs. This is the case in the present study when low CF titres are considered as positive. The CF test may thus provide useful laboratory support for comparative studies of trachoma in large population groups.