Theoretical analysis of the sensitivity of the solid phase antibody assay (ELISA)

The sensitivity of the solid phase ELISA antibody assay was analyzed from a theoretical perspective. Results show that the investigator may choose either affinity dependent or affinity independent performance by adjusting the assay conditions. High antigen concentration (concn) and small interepitope distance favor affinity independence, while low antigen concn and large interepitope distance favor affinity dependent assay behavior. The maximum sensitivity will occur in the affinity independent region. Antibody titers obtained under affinity independent conditions will reflect true antibody concn, but measurements performed under affinity dependent conditions will underestimate antibody concn.