UltramicroELISA for measuring tetanus antitoxin in human sera.

This article describes a combination of methods--a solid-phase enzyme-linked immunosorbent assay (ELISA) combined with an ultramicroanalytical system (UMAS)--that can be used to measure tetanus antitoxin activity in human sera or plasma. The test, which is rapid and permits analysis of 78 samples of serum per reaction plate with a volume of 10 microL of diluted serum per sample, is proposed as an alternative to the traditional biologic assay in mice based on seroneutralization of a known dose of tetanus toxin. The study reported here compared these two procedures, using them both to evaluate 100 sera from the Clinical Laboratory of the General Calixto García Hospital in Havana, Cuba. The two sets of results showed a high degree of correlation (r = 0.99) when subjected to linear regression analysis (95% CI = 0.985-0.993). These and other findings indicate that the cheap and rapid ultramicroELISA method can perform certain tasks for which the slower and costlier traditional assay is not well suited, such as field evaluation of tetanus toxoid vaccines and identification of hyperimmune plasmas appropriate for use in producing specific antitetanus immunoglobulin.