Entamoeba histolytica and Entamoeba dispar: Epidemiology and comparison ofdiagnostic methods in a setting of nonendemicity

Recent studies suggest that stool antigen assays are more sensitive and spe cific than microscopy for the diagnosis of Entamoeba histolytica infection, One hundred twelve patients presenting at 3 centers with symptoms or risk factors of E, histolytica infection were prospectively enrolled in this stu dy to evaluate new diagnostic tests for infections with E. histolytica and Entamoeba dispar. Four ELISA-based stool antigen kits for detecting E, hist olytica or E, dispar were blindly compared with stool microscopy. Amebic se rology was assessed by indirect hemagglutination, When antigen assays were used as the reference standard, microscopy performed at referral centers wa s more specific (68.4% vs. 9.5%) but less sensitive (70.4% vs. 92.1%) than microscopy performed in community laboratories. Diagnosis with the E. histo lytica test and Merlin Optimun S ELISA indicated that only 3 (4.2%) of 72 c oproantigen-positive stools were positive for E. histolytica. Indirect hema gglutination was a good predictor of E, histolytica infection when titers o f antibody to ameba were greater than or equal to 1 : 512.