Standardization of serological assays for parasitic diseases with schistosomiasis and toxocariasis as prototypes.

A standardized microtest plate enzyme-linked immunosorbent assay (ELISA) was developed using the microsomal fraction of adult worms of Schistosoma mansoni (MAMA) as antigen. A standard reference serum pool was prepared and arbitrarily designated as having 100 activity units per microliter. The precision of the test, the suitability as a standard of the reference serum pool, and the J index as a method of determining the significant level of reactivity were evaluated. The predictability of the assay for patients with S. mansoni infections and for non-schistosomiasis patients was 95%. Preliminary studies with the truly quantitative microtest plate kinetic ELISA indicate that this assay is suitable for standardization for schistosomiasis and toxoplasmosis. The need for WHO International Reference Sera with designated International Units and for well-defined batteries of sera for evaluating the specificity and sensitivity of assays was emphasized.