A rapid one-step method of EIA for detection of circulating antigen of Schistosoma japonicum

To establish a highly sensitive serologic method for detecting the circulating antigen of Schistosoma japonicum for the diagnosis of this disease and the evaluation of drug therapy effect.

A set of complex support made of polyvinyl-chloride (PVC) film slide, adsorbed with specific antibody, was used to test serum samples collected from cases with schistosomiasis japonica, by adding specific enzyme conjugate and substrate tetra-methyl benzidine (TMB) with 3% H2O2 in 10:0.1, developed or prepared in our laboratory. Tests were carried out with the set on cases with malaria, paragonimiasis, clonorchiasis, visceral leishmaniasis and cysticercosis as well as normal individuals as control. Serum sample of 50 microliters was used in each test and reacted with reagents at room temperature for 30 minutes. The color of positive reaction was blue while negative reaction was colorless.

Positive rate among cases with schistosomiasis japonica was 100% (45/45) in acute stage, 94.8% (530/559) in early chronic stage and 52.4% (66/126) in late stage. False positive reaction was found neither among all normal individuals (0/513), nor among cases of 155 with malaria, 120 with clonorchiasis, 24 with visceral leishmaniasis and 110 with cysticercosis, except one among 29 cases with paragonimiasis (1/29).

The rapid one-step enzyme immunoassay (EIA) to detect circulating schistosome antigen (CSA) has been well established in our laboratory with high sensitivity and good specificity as well as reproducibility. The reaction result can be read easily even in field conditions without power supply. Moreover, the assay is time-saving, simple to handle and suitable for the diagnosis of schistosomiasis japonica and evaluation of drug therapeutic effect in practice in the control program of the disease.