Comparison of Dot-ELISA with Sandwich ELISA in detecting circulating antigen in patients with bancroftian filariasis

Dot-ELISA assay was compared with standard Sandwich ELISA in detecting parasite antigen in sera from patients with bancroftian filariasis. The same monoclonal antibody and the same serum samples were used in both assays. With Dot-ELISA, 67 of 70 serum samples from microfilaremic patients were positive at a dilution of 1:50. End titers ranged from 1:80 to 1:1 280. While with Sandwich ELISA, 64 of the 70 serum samples were positive at a dilution of 1:10. End titers ranged from 1:10 to 1:320. The specificity of both assays was over 91%, but their sensitivity was markedly different. Dot-ELISA could detect as little as 0.055 ng/ml microfilarial antigen added to normal human serum, whereas the lower limit of detection by Sandwich-ELISA was 10 ng/ml parasite antigen. An additional advantage of Dot-ELISA is that it does not require radioactivity or sophisticated equipment and, therefore, can be performed in virtually all filariasis-endemic areas.