Abstract
Aims: To describe the development and evaluation of a diagnostic enzyme immunoassay (EIA) for IgM antibody to serogroup C capsular polysaccharide of Neisseria meningitidis (CCPS).
Methods: Purified CCPS was used as the antigen. The optical densities (OD) that determined the cut‐off values for the assay were derived using sera from blood bank donors, and the accuracy was evaluated with sera from patients with culture‐confirmed serogroup C and non‐serogroup C invasive meningococcal disease (IMD), other infectious diseases, culture‐confirmed pharyngeal carriage of N. meningitidis and immunoproliferative disorders.
Results: In sera collected between days 5 and 20 following positive culture, the assay had a sensitivity of 92%. The two negative sera were from a single patient but showed a significant rise in OD. The sensitivity declined to 80% on days 21–40 then to 75% on days 41–70. No positive reactions were detected in five samples collected after 71 days. The specificity of the assay was at least 97%.
Conclusions: An EIA for IgM antibody to CCPS was evaluated for local conditions and had acceptable sensitivity and specificity. Use of the assay, based on a single blood sample, provided clinically and epidemiologically relevant information for individual and public health management of IMD.