Comparison of the dot immunobinding assay and two enzyme-linked immunosorbent assay kits for the diagnosis of liver cystic echinococcosis

Abstract

The dot immunobinding assay for the detection of hydatid antigen-specific antibodies (HA-DIA) was evaluated in patients with liver cystic and alveolar echinococcosis in comparison to two commercial ELISA kits. In 30 patients, E. granulosus infection (CE) was confirmed by histopathology or by the presence of parasite protoscoleces and/or hooks or specific antigen 5 (Ag5) in cyst fluid samples obtained by the fine needle aspiration biopsy (FNAB). Infection of E. multilocularis (AE) was diagnosed in two patients by the detection of specific anti–Em2 plus ELISA and -Em18 Western blot antibodies and finally confirmed by histopathology. The HA-DIA using bovine hydatid antigens showed a high sensitivity in serum samples from CE patients; specific antibodies were found in 29 of 30 CE patients (96.7%). One negative result has been observed in a patient 2.6 years after radical surgery with a subsequent albendazole chemotherapy. The Echinococcosis ELISA® (Dialab Diagnostic) was positive in 23 CE cases (76.7%). The correlation between the HA-DIA and the Echinococcosis ELISA® was statistically significant. By contrast, Echinococcus granulosus IgG ELISA® (Bordier Affinity Products) gave positive results in only 12 of 30 CE patients (40.0%). Sera from two AE patients were high positive in all three methods analysed in our study. In non-endemic areas, due to the between-strains variations and differences in cyst immunogenic activity, related to the natural history of the parasite, a choice of an optimal method for a diagnosis of liver cystic echinococcosis has been discussed. The high diagnostic sensitivity and a faster one-step procedure, in comparison to traditional enzyme immunoassays, make the HA-DIA a very useful method for the diagnosis of CE in non-endemic areas, especially in a case of small or degenerating lesions and sterile echinococcal cysts with a low immunogenicity. The positive serology for CE frequently requires additional differentiation with E. multilocularis-specific antibodies.