title: Diagnostic parameters of serological ELISA for invasive amoebiasis, using antigens preserved without enzymatic inhibitors.
abstract: Amoebiasis is the third cause of death due to parasites in the world. Although, numerous serodiagnostic and salivary tests have been developed, the majority of these assays lack sensitivity in endemic zones to detect acute amoebic liver abscess. The two main limiting factors to develop reliable assays are the high levels of anti-amoeba antibodies in populations living in endemic zones, and the proteolysis of amoebic extracts even treated with inhibitors. Our group reported a method to preserve amoebic antigens without using enzymatic inhibitors (IC:MC fraction) that shows stability for years. Here we describe the development of a serologic ELISA to diagnose amoebiasis made with IC: MC antigens, and its validation for clinical use in endemic areas. In our study, we included sera from 66 patients diagnosed with acute amoebic liver abscess and 33 volunteers living in an endemic area for amoebiasis. Our assay was compared with an indirect haemagglutination assay (IHA) an ELISA elaborated with antigens derived from untreated trophozoites. The ELISA made with IC: MC antigens presented more reproducibility compared to other assays. Sera from 95% ALA patients showed a positive value. The ELISA (IC: MC) detected 97% of patients with ALA compared to an 81% using IHA. The parameters of ELISA (vs. IHA) were Sensitivity 98% (81%), Specificity 96% (97%), Positive predictive value 98% (96%), Negative predictive value 96% (73%) and Accuracy 98% (87%). A negative serologic test does not rule out the diagnosis of invasive amoebiasis. The ELISA made with antigens preserved without using enzymatic inhibitors has valuable serodiagnostic value to diagnose acute amoebic liver abscess, even in populations living in endemic zones of amoebiasis carrying antibodies against amoebas. In conclusion, ELISA-IC:MC presented better diagnostic parameters than IHA although a negative serologic test does not rule out acute invasive amoebiasis.
authors.affiliation: Instituto de Biotecnología, Facultad de Ciencias Biológicas, Mexico. Electronic address: maria.floresgz@uanl.edu.mx.
authors.forename: María S
authors.initials: MS
authors.lastname: Flores
authors.affiliation: Departamento de Microbiología, Facultad de Medicina, Universidad Autónoma de Nuevo León, Monterrey, Mexico.
authors.forename: Perla
authors.initials: P
authors.lastname: Carrillo
authors.affiliation: Departamento de Microbiología, Facultad de Medicina, Universidad Autónoma de Nuevo León, Monterrey, Mexico.
authors.forename: Eva
authors.initials: E
authors.lastname: Tamez
authors.affiliation: Houston Methodist Research Institute, Houston, TX, USA.
authors.forename: Roberto
authors.initials: R
authors.lastname: Rangel
authors.affiliation: Departamento de Microbiología, Facultad de Medicina, Universidad Autónoma de Nuevo León, Monterrey, Mexico.
authors.forename: Elba G
authors.initials: EG
authors.lastname: Rodríguez
authors.affiliation: Instituto de Biotecnología, Facultad de Ciencias Biológicas, Mexico.
authors.forename: María G
authors.initials: MG
authors.lastname: Maldonado
authors.affiliation: Unidad de Investigación Médica en Inmunoquímica, Hospital de Especialidades, Centro Médico Nacional Siglo XXI, Instituto Mexicano del Seguro Social, México, DF, Mexico.
authors.forename: Armando
authors.initials: A
authors.lastname: Isibasi
authors.affiliation: Instituto de Biotecnología, Facultad de Ciencias Biológicas, Mexico.
authors.forename: Luis
authors.initials: L
authors.lastname: Galán
mesh_terms: D000818:Animals; D000909:Antibodies, Helminth / Q000097:blood*; D000947:Antigens, Helminth / Q000276:immunology*; D016022:Case-Control Studies; D004446:Echinococcus / Q000276:immunology / Q000302:isolation & purification*; D004791:Enzyme Inhibitors; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000592:standards*; D006801:Humans; D007132:Immunoglobulin Isotypes / Q000097:blood; D008101:Liver Abscess, Amebic / Q000175:diagnosis* / Q000276:immunology; D011309:Preservation, Biological; D013997:Time Factors
chemical_list: D000909:Antibodies, Helminth; D000947:Antigens, Helminth; D004791:Enzyme Inhibitors; D007132:Immunoglobulin Isotypes
keywords: Amoebiasis; Antigens; Diagnosis; ELISA; Entamoeba histolytica; Enzymes