[Ultramicro-ELISA for measuring tetanus antitoxin in human serum]

A solid-phase enzyme immunoassay (ELISA) for measuring tetanus antitoxin activity in human serum is described; the assay is based on a combination of the indirect method and ultramicro analysis. This rapid test, which has the capacity to analyze 78 blood samples per reagent plate (at a volume of 10 microL of diluted serum per sample), is proposed as an alternative to the traditional mouse bioassay system based on the neutralization of a known dose of tetanus toxin. Results from both tests showed a high correlation in the lineal regression analysis (r = 0.99; CI95%: 0.985 to 0.993). It is recommended that the ultramicro ELISA assay be used in the field to evaluate tetanus toxoid vaccines and to identify hyperimmune plasmas suitable for producing antitetanus immunoglobulin.