title: Negative-ELISA using native and filtrated cystic fluid antigens to rule out cystic echinococcosis.
abstract: An increasing number of cases of echinococcosis in Thailand have been imported, probably native infections and medical transfers. Serodiagnosis is one diagnostic choice for interpreting infections before a further step is done. Due to limited antigen, indirect ELISA has been used as a negative screening test for IgG-detection to rule out echinococcosis. Native hydatid cystic fluid (HCF) antigen from Belgium was used for such testing, in which the ODs-ELISA of samples were compared with those of two positive controls. Subsequently, hydatid cyst fluid from a Thai patient was obtained and the filtrated cyst fluid antigen [(<30)-(>10) kDa, HCF30.10] was prepared to develop negative screening results for the serum samples. By using HCF, three of twenty-four samples resulted in higher ODs-ELISA than the controls. In an attempt to observe the cross-reactivity of this native antigen, IgG-antibodies from many helminthiases cross-reacted and showed high ODs-ELISA. The HCF30.10 Ag was used to develop the test and analyze IgG-antibodies from 5 positive controls (2 parasite-confirmed and 3 positive-serodiagnosed), 183 heterologous cases of 29 diseases and 50 healthy control sera. At a cut-off value of 0.484, the test had 100% sensitivity and 42% specificity. Only Malayan filariasis, onchocercosis, fascioliasis, amebiasis, giardiasis and blastocystosis gave true negatives. Antibodies from nematodiases strongly cross-reacted with HCF30.10 Ag. Nine of fifty (18%) healthy serum controls produced higher OD-values than the cut-off. The routine ELISA uses the HCF30.10 Ag to produce a negative result to echinococcosis, because limited cystic fluid antigen (Thai patient) for test improvement, a lot of cross-reactions and only two protoscolex-positive controls are available.
authors.affiliation: Department of Helminthology, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Bangkok 10400, Thailand. tmpdk@mahidol.ac.th
authors.forename: Paron
authors.initials: P
authors.lastname: Dekumyoy
authors.forename: Doungrat
authors.initials: D
authors.lastname: Riyong
authors.forename: Wallop
authors.initials: W
authors.lastname: Pakdee
authors.forename: Jitra
authors.initials: J
authors.lastname: Waikagul
mesh_terms: D000818:Animals; D000941:Antigens; D000947:Antigens, Helminth / Q000276:immunology*; D016022:Case-Control Studies; D002589:Cestoda / Q000276:immunology; D004443:Echinococcosis / Q000175:diagnosis* / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D006801:Humans; D012698:Serologic Tests / Q000379:methods*
chemical_list: D000941:Antigens; D000947:Antigens, Helminth