Serological diagnosis of amoebiasis by immunofluorescence.

A positive serological diagnosis of amoebiasis could be made by immunofluorescence in 66 of 78 established cases, taking a serum titre of 16 or higher as diagnostic: at this level there were no false positives among 94 control sera. The test is simple and may be carried out on amoebic smears stored for several months in 2-octanol. The serological activity is largely confined to the IgG immunoglobulin fraction and is specific for Entamoeba histolytica; cross reactions were not detected with other protozoa. Gel diffusion serological analysis permitted a positive diagnosis of amoebiasis in 60 of the 78 cases, and, combining this with the immunofluorescence test, raised the diagnostic score to 71 cases.