Diagnostic Accuracy of Indirect Immunofluorescence Assay for Intestinal Invasive Amebiasis and Impact of HIV Infection in a Non-endemic Country

To diagnose amebic colitis (AC), serologic tests have the advantage of being inexpensive, noninvasive, and easy to perform, but few studies have investigated their utility, especially in a non-endemic country. A total of 299 symptomatic patients (165 HIV-infected patients) who underwent endoscopy and indirect immunofluorescence (IF) assay were analyzed between 2003 and 2009. The diagnosis of AC was defined as detection of amebic trophozoites from biopsy specimens or intestinal fluid sample via endoscopy. Forty-five patients (29 HIV-infected patients) were diagnosed with AC. The area under the receiver-operating characteristic curve (ROC-AUC) for the IF assay was excellent (0.90), and a cut-off value of 100 provided 89% sensitivity and 87% specificity. ROC-AUC was slightly lower in patients with HIV infection (0.88) than in those without HIV infection (0.94). Among HIV-infected patients, ROC-AUC showed no significant differences between different CD4+ cell counts. The IF assay is useful for diagnosing AC in symptomatic patients with and those without HIV infection.