DOT-ELISA IN THE DIAGNOSIS OF SCHISTOSOMIASIS

Preliminary results with Dot-ELISA, a technic originating in China, show that no false positive reactions are obtained among 65 normal controls, while the positive rates of 63 schistosomiasis cases were 88.9-96.8%, with a certain degree of cross reaction between clonorchiasis and paragonimiasis patients. Compared to plate-ELISA, Dot-ELISA requires higher concentrations of HRP-conjugate but the quantity of reagents needed is much less. Positive color dots on the nitrocellulose forming after using 3,3 diaminobenzidine, can be maintained for quite long periods. 4-chloro-1-naphthol generates a blue color which fades more quickly. Since the antigen-reactivity of dried antigen bound nitrocellulose stored at 4 C can be maintained for at least 4 weeks and the quality of China-made nitrocellulose is practically comparable to that of the imported variety, it seems reasonable to suggest extensive use cf the technic for supplementary diagnosis of schistosomiasis. As to substrates, 4-chloro-1-naphthol is devoid of carcinogenicity and positive reactions are indicated by clearly visible blue dots against an almost colorless background. 3,3 diaminobenzidine is more commonly used and its color reaction lasts longer.