Abstract: Objectiv To evaluate the usefulness of dot immuno-gold filtration assay（DIGFA） for the diagnosis of Paragonimus infection. Methods During 2003 to 2006, 72 cases suspected of paragonimiasis in Zhejiang Province were examined with DIGFA for rapid detection of specific antibodies against Paragonimus (Pw-DIGFA). The diagnosis was primarily established with the presence of antibodies, experience of ingesting raw freshwater crabs or crayfishes and clinical presentations. The cases were treated with praziquantel and followed-up at 3 and/or 6 months post-treatment. Antibody level in patients (pre- and post-treatment) were detected in parallel and analyzed comparatively by Pw-DIGFA and ELISA. Results The result of detection by Pw-DIGFA was in agreement with that of ELISA. 28 of 72 cases were antibody positive and 44 cases were negative. Among the 28 positives, 26 cases had a history of eating raw freshwater crab or crayfishes and the other 2 cases drank freshwater from brook before. 21 cases showed paragonimiasis-related clinical symptoms such as low-grade fever, cough, or changes in image examination, while the other 7 cases showed only eosinophilia in peripheral blood (15％-70％). The mean absorbance values (A₄₅₀) of positive sera, negative sera and normal sera tested by ELISA were 1.7361, 0.2973 and 0.2657 respectively. There was significant difference between the positive cases and the negative cases (t=12.047, P<0.01) and no significant difference between the negative cases and normal controls （t=1.919, P>0.05）. At 3 month post-treatment, serum antibody in 5 cases whose clinical symptoms and physical signs relieved or disappeared decreased 2-5 titers and that of one case who relapsed with new signs increased by one titer. In Pw-DIGFA, the dot color of 5 cured cases showed a little weaker than that of pre-treatment and the relapsed case displayed similar response. At 6 month post-treatment, 7 sera of clinically cured cases showed significantly weaker response than that of pre-treatment. The antibodies of those sera dropped 3-6 titers. Conclusion Pw-DIGFA is of supplementary value for clinical diagnosis of paragonimiasis. Antibody detection by pre- and post-treatment using Pw-DIGFA shows potential for the evaluation of therapeutic effect.

Key words: Paragonimiasis, Dot immuno-gold filtration assay, Antibody, Diagnosis, Evaluation of therapeutic effect