Rapid detection of specific IgM against Schistosoma japonicum by dot immuno-gold filtration assay

Objective To evaluate the effect of diagnosis and treatment by detecting specific IgM of schistosomiasis japonica with dot immuno-gold filtration assay (DIGFA). Method The DIGFA for detecting IgM of schistosomiasis (IgM-DIGFA) was developed by using soluble egg antigen (SEA) and sheep anti-human IgM immuno-gold conjugate. Conventional DIGFA for detecting IgG (IgG-DIGFA) was applied as the parallel control for evaluating the effect of diagnosis and treatment by detecting different kinds of sere. Results Detecting serum of acute and chronic schistosomiasis, the positive rate of IgM-DIGFA were 100% (25/25) and 95.8% (69/72) respectively, and the positive rates of IgG-DIGFA were 100% (25/25) and 97.2% (70/72) respectively. There are no statistical differences between two assays( P > 0.05). The specificities of two assays were 99% and 100% respectively. The cross-reaction of IgM-DIGFA was lower. Compared with IgG-DIGFA, only 3.3% specimen of patient infected with paragonimus westermani was positive. The rates of negative turning of IgM-DIGFA in chronic schistosomiasis at the 6th month and 12th month intervals after treatment were 65.2% (15/23)and 88.0% (22/25)respectively. The rates of negative turning of IgG-DIGFA were 21.7%(5/23)and 64.0%(16/25) respectively. Conclusions It is sensitive and specific to detect IgM with DIGFA, as to detect IgG. IgM-DIGFA is also good for evaluating the treatment of schistosomiasis. Key words: Schistosomiasis japonica; Dot immunogold filtration assay; IgM;  Diagnosis