Comparison of the serological tests ICT and ELISA for the diagnosis of alveolar echinococcosis in France

Parasite 2014, 21, 34 Ó J. Knapp et al., published by EDP Sciences, 2014 DOI: 10.1051/parasite/2014037 Available online at: www.parasite-journal.org RESEARCH ARTICLE OPEN ACCESS Comparison of the serological tests ICT and ELISA for the diagnosis of alveolar echinococcosis in FranceI Jenny Knapp1,2,*, Yasuhito Sako3, Frédéric Grenouillet1,2,4, Solange Bresson-Hadni2,5, Carine Richou2,5, Houssein Gbaguidi-Haore1,6, Akira Ito3, and Laurence Millon1,2,4 1 2 3 4 5 6 Laboratory of Chrono-environnement, UMR/CNRS 6249, Faculty of Medicine and Pharmacy, Besançon, France WHO Collaborating Centre for prevention and treatment of human echinococcosis, Besançon, France Department of Parasitology, Asahikawa Medical University, Asahikawa, Hokkaido, Japan Laboratory of Parasitology-Mycology, University Hospital of Besançon, France Department of Hepatology, University Hospital of Besançon, France Laboratory of Hospital Hygiene, University Hospital of Besançon, France Received 18 October 2013, Accepted 4 July 2014, Published online 25 July 2014 Abstract – Serological diagnosis of alveolar echinococcosis (AE) is a key element for efficient patient treatment management. A rapid immunochromatography test kit (ICT) using the recombinant Em18 antigen (rEm18) was recently developed. The aim of our study was to assess this test on a panel of sera from French patients with alveolar echinococcosis and control patients. In a blind test, a total of 112 serum samples were tested including samples of AE (n = 30), cystic echinococcosis [CE] (n = 15), and polycystic echinococcosis [PE] (n = 1). For the comparison, 66 sera from patients with hepatocarcinoma, fascioliasis, toxocariasis, Caroli’s disease, or autoimmune chronic active hepatitis were used. The diagnostic test sets we used were the rEm18-ICT and two validated ELISAs with rEm18 and Em2Em18 antigens, respectively. For the ICT, 27/30 sera from AE patients, 4/15 sera from CE patients and the PE patient serum were positive. One serum from the control panel (toxocariasis) was positive for the ICT. The rEm18-ICT sensitivity (90.0%) and specificity (92.7%) for detection of Em18-specific antibodies confirmed it as a relevant tool for AE diagnosis. The rEm18-ELISA had a sensitivity of 86.7% and specificity of 91.5%, and the Em2-Em18-ELISA had a sensitivity of 96.7% and specificity of 87.8%. However, when AE patient sera are recorded as weak in intensity with the ICT, we recommend a double reading and use of a reference sample if the ICT is used for patient follow-up. Key words: alveolar echinococcosis, diagnosis, rEm18, immunochromatography, rapid test, rEm18-ELISA and Em2-Em18-ELISA tests. Résumé – Comparaison des tests sérologiques ICT et ELISA pour le diagnostic de l’échinococcose alvéolaire en France. Le diagnostic sérologique de l’échinococcose alvéolaire (EA) est un point fondamental pour assurer l’organisation du traitement du patient. Un test rapide immuno-chromatographique (ICT), utilisant l’antigène recombinant Em18 a été récemment développé. Le but de cette étude était d’évaluer ce test sur un panel de sérums de patients français présentant une échinococcose alvéolaire et sur des patients de contrôle. Lors d’un test réalisé en aveugle, un total de 112 sérums a été testé, regroupant des échantillons d’EA (n = 30), d’échinococcoses kystiques (EK) (n = 15) et d’échinococcose polykystique (EP) (n = 1). Pour comparaison, 66 patients présentant un hépatocarcinome, une distomatose, une toxocarose, une maladie de Caroli ou une hépatite active chronique autoimmune ont été utilisés. Les tests diagnostiques employés étaient l’ICT rEm18 et deux tests ELISA validés utilisant respectivement les antigènes rEm18 et Em2-Em18. Avec l’ICT, 27/30 sérums de patients EA, 4/15 EK et le patient EP étaient positifs. Un sérum du panel contrôle (toxocarose) présentait un ICT positif. Pour le test ICT rEm18, la sensibilité (90,0 %) et la spécificité (92,7 %) pour la détection de l’antigène Em18 confirme que ce test est un outil fiable pour le diagnostic d’EA. L’ELISA rEm18 présentait une sensibilité de 86,7 % et une spécificité de 91,5 %, et l’ELISA Em2-Em18 une sensibilité de 96,7 % et une spécificité de 87,8 %. Néanmoins lorsque des sérums de patients présentent une bande test d’intensité faible pour l’ICT nous recommandons une double lecture et l’emploi d’un échantillon de référence pour une utilisation en suivi. *Corresponding author: Innovation for the Management of Echinococcosis. Invited editors: Dominique A. Vuitton, Laurence Millon, Bruno Gottstein and Patrick Giraudoux I This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2 J. Knapp et al.: Parasite 2014, 21, 34 Introduction In rodents and humans, alveolar echinococcosis (AE) appears as a tumor-like lesion and is caused by accidental ingestion of eggs of the cestode Echinococcus multilocularis, a fox tapeworm. The adult worm produces eggs which are released into the environment with fox feces. The parasite is widely present in the Northern Hemisphere in countries such as China, where the estimated prevalence ranges from 0.2% to 9% in 12 regions [22]. The parasite is also present in temperate Europe, where a total of 559 human cases have been identified in nine countries [9, 14]. A recent increase in reported cases of human AE and of E. multilocularis in wild animals has been observed not only in historically endemic regions in Europe [6, 20], but also in new endemic regions [5, 23]. In France, from 1982 to 2009, 8 to 29 new cases per year, mostly in the Northeast, were identified by the FrancEchino network [12]. The exposure to eggs is likely due to repeated contact with wild or domestic carnivores such as foxes, dogs, and cats [21], consumption of wild berries or raw vegetables growing close to the ground, and agricultural activities [3]. The main AE symptoms are abdominal pain, asthenia, and hepatomegaly. Generally, the first symptoms appear 5–15 years after contamination [1, 3]. Diagnosis is often made based on images obtained by ultrasound, computerized tomography, or magnetic resonance imaging [4]. Immunodiagnosis tests, e.g., the enzyme-linked immunosorbent assay (ELISA) using rEm18 (rEm18-ELISA) [18] or rEm18 plus the native Em2 antigen purified from E. multilocularis larvae (Em2-Em18-ELISA) (Bordier Affinity, Crissier, Switzerland), are currently being used in laboratories. Indirect hemagglutination (IHA) (Hydatidose Fumouze kit, Fumouze Diagnostics, Levallois-Perret, France) is one of the low-cost screening techniques [11], and the Western blot technique (WB) (LDBIO Diagnostics, Lyon, France), using a whole E. multilocularis larval antigen, is the confirmation technique for species diagnosis [4, 16]. In 2003, Xiao (...truncated)