RT Journal Article SR Electronic(1) A1 Melville-Smith, M. A1 Balfour, A.YR 1988 T1 Estimation of Corynebacterium diphtheriae antitoxin in human sera: a comparison of an enzyme-linked immunosorbent assay with the toxin neutralisation test JF Journal of Medical Microbiology, VO 25 IS 4 SP 279 OP 283 DO https://doi.org/10.1099/00222615-25-4-279 PB Microbiology Society, SN 1473-5644, AB 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., UL https://www.microbiologyresearch.org/content/journal/jmm/10.1099/00222615-25-4-279