Detection of the Adhesin Antigen in Stool for the Diagnosis of Entamoeba histolytica with the Enzyme Linked Immunosorbent Assay (ELISA) Method

Aim: Entamoeba histolytica (E. histolytica) and E. dispar are morphologically identic but they are genetically distinct according to their immunological, molecular biological and biochemical characteristics. E. histolytica is the invasive species that leads to amoebic colitis and liver abscesses and E. dispar which exerts non-invasive features. Especially laboratory technicans who are not experienced enough can confuse the E. histolytica/dispar with leukocytes, macrophages and other trophozoites under direct microscopy. However, since E. histolytica is the reason for amoebic dysentery cases, certain and accurate diagnosis is very crutial in order to plan the treatment. In our study, we have used the ELISA technique which depends on searching the E. histolytica adhesin antigen in stool to bring this technique for the routine detection and diagnosis. Materials and Methods: For the study, native-lugol method and trichrome staining was conducted with 553 stool samples that were sent to laboratory for the routine parasitological examination. Samples were examined microscopically. Stool samples which showed microscopic E. histolytica/dispar cysts, presence of adhesin antigen was examined by using specific monoclonal ELISA (E. HISTOLYTICA II Techlab, Blacksburg VA 24060, USA) technique. Fisher's exact test was used for statistical analysis. Results: There were E. histolytica/E. dispar cysts and/or trophozoite structures in 22 stool samples (3.9%) with trichrome staining out of 29 stool samples (5.2%) in which E. histolytica/E. dispar cysts and/or trophozoite structures had already been detected according to native-lugol method. Adezin antigen was detected in 15 stool samples (2.7%) according to ELISA technique. With respect to trichrome staining, the detected sensitivity was found as 86.6%, specificity as 35.7%, positive predictive value as 59% and negative predictive value as 71% according to ELISA method. Statistically significant difference was detected between the two methods regarding the diagnosis of invasive E. histolytica; p < 0.05. Conclusion: Eventually, monoclonal ELISA technique which specifically detects the E. histolytica adhesin antigen and distinguishes the pathogenic E. histolytica from non-pathogenic E. dispar should be used to decrease the unnecessary treatments.