Serodiagnosis of amoebic abscess: a retrospective diagnostic accuracy study of kits marketed in Europe.

Amoebiasis is a cosmopolitan parasitic disease caused by Entamoeba histolytica. The most lethal form is extra-intestinal amoebiasis, mainly manifesting as liver abscesses. Diagnosis is based on clinical, radiological, and biological tests. However, there are currently few serology reagents still available on the European market for in vitro diagnosis, and comparative studies of existing reagents are required. We evaluated the performances of the four currently available reagents, either as standalone tests or in combination. Two enzyme-linked immunosorbent assays (ELISAs) for the detection of E. histolytica IgG were assessed: one manufactured by Bordier and the other by NovaTec. Additionally, an indirect hemagglutination technique, ELI.H.A Amoeba, and a latex particle agglutination technique, ELITex Bicolor Amoeba, both produced by ELITech Microbio, were evaluated. A total of 442 serum samples were selected from a shared centralized biobank of seven university hospitals in France. The samples included 79 from patients with amoebic abscess, 13 with amoebic colitis, and 350 from healthy donors and patients with parasitic and non-parasitic diseases, especially liver disease and immune dysfunction. The sensitivity of the four kits ranged from 87.3% to 97.5%, while their specificity ranged from 78.3% to 98.6%. Bordier ELISA demonstrated the highest sensitivity, while ELITex Bicolor Amoeba latex reagent exhibited the highest specificity. The combination of Bordier ELISA and/or ELI.H.A Amoeba for screening, combined with ELITex Bicolor Amoeba for confirmation of positive screening results, yielded the most optimal performance. This study highlights the benefits of large comparative studies of commercial assays to guide clinical microbiologists in their choices.

Importance: Amoebiasis caused by Entamoeba histolytica is common in countries with low socio-economic levels. The most lethal form is extraintestinal amoebiasis, mainly liver abscesses, which require rapid and accurate diagnosis. Diagnosis is based on clinical, radiological, and, most importantly, serological tests. Implementing a diagnostic strategy requires both knowledge of how diagnostic tests compare with each other and thorough cross-validation. To help the clinical microbiologist choose a serological reagent, we evaluated the performance of four serological reagents currently available on the European market using a large biobank of sera from seven French university hospitals. In addition to patients with amoebic abscess and healthy donors, our study included many samples from patients with other parasitic and non-parasitic pathologies (liver diseases, immune dysfunctions) in order to study particularly non-specific reactivities.