A dot immunobinding assay (DIA) on nitrocellulose membrane for the serological detection of antibodies to Entamoeba histolytica.

A rapid, cheap, simple and specific serological test of adequate sensitivity for detecting IgG antibodies against Entamoeba histolytica antigen is described. Axenically cultured amoebic antigen was used to precoat the nitrocellulose membrane. The strips were incubated with test samples and later with horseradish peroxidase (HRPO) labelled protein-A conjugate. A dark blue spot was obtained by treatment with peroxidase substrate, 4-chloro-1-naphthol, in positive samples. Serum samples from 32 healthy controls, 45 patients with acute amoebic liver abscess and 10 asymptomatic E. histolytica cyst passers were tested. This test was positive in 93% of cases of amoebic liver abscess, 3% of healthy controls and none of the cyst passers; its sensitivity (97%) and specificity (93%) were as good as that of the ELISA test and, because it is simple, quick and cheap it is recommended as a serological test of choice for the diagnosis of invasive amoebiasis.