Evaluation of the Methods Used for the Detection of Entamoeba histolytica in Stool Samples of Patients with Diarrhea

Abstract

Amoebic dysentery (amebiasis) is a parasitic infection caused by Entamoeba histolytica. The diagnosis of invasive amebiasis has traditionally been based on direct and stained microscopic examination of stool samples. Stool microscopy exhibits low sensitivity and it is difficult to distinguish E.histolytica cysts and trophozoites from cells such as leukocytes, macrophages and non-pathogenic Entamoeba species in the stool by microscopy. Therefore more sensitive and specific diagnostic methods such as enzyme linked immunosorbent assay (ELISA) tests which investigate the presence of E.histolytica-specific antigen in stool, and polymerase chain reaction (PCR) are being widely used. In this study it was aimed to study stool samples of the patients who applied with the clinical signs of amebiasis by using direct and permanent stained microscopy, E.histolytica adhesin antigen ELISA test and real-time PCR-based BD Max Enteric Parasite Panel (BD Max EPP) test and to evaluate the diagnostic values of these tests. A total of 546 faecal samples with blood and/or mucus were analyzed in the study. In these samples, the presence of E.histolytica was investigated by direct and permanent stained microscopy, E.histolytica adhesin antigen ELISA and BD Max EPP PCR. Of the samples 36.3% were suspected to contain E.histolytica/dispar/moshkovskii cyst and/or trophozoite by direct microscopic examination. Trichrome staining was performed on these samples and 49 samples were found suspicious for the presence of E.histolytica/dispar/moshkovskii cysts and/or trophozoites. The presence of E.histolytica and other Entamoeba species was not confirmed in 75.2% of the samples. BD Max EPP PCR and E.histolytica adhesin antigen ELISA tests were studied in 49 faecal samples that were suspected by trichrome staining. None of these samples were positive by ELISA. Forty-four samples were negative by PCR and invalid test results were obtained in five samples. In this study, E.histolytica was not detected in the patient population. The results of this study showed that microscopic examination alone is not sufficient for the detection of E.histolytica. It is concluded that it is necessary to use a more sensitive and specific also rapid diagnostic test such as E.histolytica-specific antigen detection test or PCR in the diagnosis of amebiasis to avoid misdiagnosis and unnecessary treatment of patients.