Evaluation of purified antigen fraction in the immunodiagnosis of cystic echinococcosis.

Echinococcus granulosus antigen B fraction (AgB) was evaluated for its prognostic value in the serological follow-up of cystic echinococcosis (CE), compared to crude hydatid fluid (HF) as well as soluble somatic Echinococcus multilocularis antigen (Em). The sensitivity and specificity of enzyme-linked immunosorbent assays (ELISA) were compared examining 177 sera from patients with different clinical courses and outcome of CE and with other parasitic infections. AgB-ELISA in comparison to confirmed cystic echinococcosis has 96.4% sensitivity and 97.2% specificity, with 93.1% positive predictive value and 98.6% negative predictive value. The HF-ELISA was more sensitive than the AgB-ELISA, but its specificity was lower. Our results indicate that AgB-ELISA was more satisfactory for seroconfirmation of acute echinococcosis than HF-ELISA. Moreover, the AgB-ELISA has a potential key role in control measures implemented in patients undergoing surgery. In sera of patients more than 3 months after the treatment, no antibody response to antigen B was detected; however, with conventionally used HF-ELISA, they were still positive. The AgB is recommended for the confirmatory diagnosis. AgB-WB allocated low background with typical "triplet" bands at 8-12-16 kDa.