Abstract: 　Objective To explore the factors of false negative antibody response in patients with echinococcosis granulosus (Eg) for improving immunodiagnosis. Methods Indirect ELISA and sandwich ELISA were used to detect the specific antibody of IgG subclass (IgG1, IgG2, IgG3, IgG4) and IgA, IgM, IgE, as well as circulating antigen (CAg) and immunocomplex (CIC) in sera of Eg patients with negative response of total IgG. Results Among 42 sera with IgG negative seroresponse, 32 were positive with IgG subclass, IgA, IgM or IgE antibody, 10 were negative in all 7 kinds of antibody response. The detection rate of specific IgG1, IgG4, IgA, IgM and IgE was 42.9%, 11.9%, 28.6%,26.2%and 21.4% respectively, being significantly higher than in sera of the control. IgM level in children was higher than that in adults. IgG subclass in patients with liver Eg was higher than that of pulmonary hydatidosis, when testing with IgG1 combined one or two of the other six Ig antibodies. The highest positive rate (64.3%) was seen in IgG1+IgA+IgM antibody system. The positive rate of CAg and CIC in IgG negative patients was 28.57% and 30.95%, respectively. Conclusion The factors involved with seronegative response of total IgG in Eg patients might be low specific IgG, variant Ig antibody expression and formation of CIC. Combined detection of IgG1+IgA+IgM could enhance the sensitivity of serological tests in Eg patients.

Key words: echinococcosis granulosus, antibody, antigen, circulating immunocomplex, diagnosis