%0 Journal Article %A Melville-Smith, M. %A Balfour, A. %T Estimation of Corynebacterium diphtheriae antitoxin in human sera: a comparison of an enzyme-linked immunosorbent assay with the toxin neutralisation test %D 1988 %J Journal of Medical Microbiology, %V 25 %N 4 %P 279-283 %@ 1473-5644 %R https://doi.org/10.1099/00222615-25-4-279 %I Microbiology Society, %X Summary. Serum samples from 101 individuals were titrated for Corynebacterium diphtheriae antitoxin by an IgG-specific enzyme-linked immunosorbent assay (ELISA) and a neutralisation test in tissue culture (TC). In some of the sera, the concentrations of antitoxin determined by the two assays were different; antitoxin values in these sera were titrated again by neutralisation tests in guinea pigs (GNT). Antitoxin concentrations of >0·01 IU/ml by GNT partly corresponded to values obtained in both ELISA and TC. Only the values from TC agreed with lower GNT results. Heat inactivation of sera was investigated and rejected as a possible reason for the discrepancy in the results. ELISA can be used to detect levels of < 0·1 IU/ml, although the accuracy below 0·01 IU/ml, often considered a protective level, is questionable. At higher levels ELISA was reproducible for the titration of diphtheria antitoxin in human sera and offers a useful alternative to both in-vivo assays and TC. %U https://www.microbiologyresearch.org/content/journal/jmm/10.1099/00222615-25-4-279