Alveolar hydatid disease is a serious and often fatal condition caused by infection with the metacestode form of Echinococcus multilocularis. Sera of 21 patients with histologically confirmed disease were tested by an enzyme-linked immunosorbent assay (ELISA) using a semi-purified E. multilocularis antigen fraction (Em2) and by indirect hemagglutination (IHA) and double diffusion (DD5) tests using antigens prepared from E. granulosus cyst fluid. At diagnosis, sera from all 21 patients were positive by Em2 ELISA, 18 (86%) by IHA, and 5 (24%) by DD5.
Em2 ELISA detected an antibody response earlier than IHA in 4 of 9 patients from whom sera were available before diagnosis. Following complete surgical resection, Em2 ELISA converted from positive to negative in serum of 2 of 3 patients, while IHA results did not change. Following incomplete resection, 14 of 15 patients tested remained positive by Em2 ELISA, while 12 remained positive by IHA. Of sera from 361 healthy persons from regions free of E. multilocularis, none were positive by Em2 ELISA, while 8% were positive by IHA. Of sera from 59 patients with non-echinococcal parasitic infections, none were positive by Em2 ELISA, while 31% were positive by IHA. Thus, in comparison with tests using E. granulosus antigens, Em2 ELISA appears to be more sensitive and specific for diagnosing AHD, useful on follow-up of resected patients, and positive earlier in the course of disease.