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Dissociation Of Immune Complexes In Serum Samples Improves Detection Of Circulating Parasitic Antigens

1Kesmat M Maher and 2Hala S El-Wakil

1Department of Immunology, Theodor Bilharz Research Institute and 2Department of Parasitology, Faculty of Medicine, Ain Shams University, Cairo, Egypt.

A biotin-avidin double sandwich enzyme linked immunosorbent assay (B-A ELISA) for detection of circulating antigens (CAg-ELISA) Schistosoma mansoni, Echinococcus granulosus and Fasciola hepatica was developed using polyclonal antibodies. The effect of boiling of Di-Na EDTA treated serum on the sensitivity and specificity of this assay was assessed. The assay was compared with an ELISA assay for detection specific IgG antibodies. Serum samples from patients with schistosomiasis (n= 36), hydatidosis (n= 42) and fascioliasis (n= 26) and from healthy individuals (n= 23) and patients with other parasitic diseases (n= 20) were included. The results revealed that C.Ag ELISA has a sensitivity of 52.7%, 40.4% and 65.3% before boiling as compared to 61.1%, 59.5% and 73% after boiling in schistosomiasis, hydatidosis and fascioliasis sera, respectively. However, the specificity and positive predictive value was 100%. On the other hand, the IgG-ELISA gave 69.4%, 69%, 80.7% sensitivity rates and 74%, 82.6%, and 82.6% specificity rates, in schistosomiasis, hydatidosis and fascioliasis sera, respectively. In addition, there was a significant correlation between the results of B-A C.Ag ELISA and IgG ELISA (P<0.01) in diagnosis of schistosomiasis, hydastidosis and fascioliasis. It is concluded that Di-Na EDTA treatment and boiling of sera improves the detection of circulating hydatid and Fasciola hepatica antigens, and that polyclonal antibodies can be used for detection of parasitic circulating antigens in a fairly good percentage of patients with active infection. These findings are of economic importance in developing countries.