Investigation of enzyme immunoassay time courses: Development of rapid assay systems

An enzyme immnoassay (EIA) consists of a series of antigen-antibody reactions which result in the binding of an enzyme-labeled antibody to a solid phase. The performance time of an EIA determination is thus largely dependent upon the time required for the antigen-antibody reactions. In an attempt to develop a rapid EIA system, we investigated the time course of an EIA system for the measurement of Haemophilus influenzae type b polysaccharide. We found that, although the use of short incubations led to a decrease in sensitivity, an assay system utilizing 10-min incubation periods was still capable of detecting antigen at a concentration of 1 ng/ml. Important factors in the sensitivity of EIAs with short incubation times were the performance of the reaction at 37°C and the incubation of the solid phase with constant agitation. Utilizing these techniques, we developed an EIA system for the measurement of H. influenzae type b polysaccharide which could be completed in less than 30 min. This system was sufficiently sensitive to detect H. influenzae polysaccharide in the cerebrospinal fluids of nine patients with proven H. influenzae meningitis. Thus, EIA systems utilizing short incubation times might be useful for the rapid detection of infectious antigens in body fluids.