Enhanced serological diagnosis of invasive meningococcal disease by determining anti-group C capsule IgM antibody by enzyme immunoassay.
OBJECTIVE
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.
Lahra
Monica M
MM
Department of Microbiology, South Eastern Area Laboratory Services, Prince of Wales Hospital, Randwick, New South Wales, Australia.
Robertson
Peter W
PW
Whybin
Ross
R
Tapsall
John W
JW
D000907:Antibodies, Bacterial / Q000097:blood*; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods*; D007075:Immunoglobulin M / Q000276:immunology*; D008589:Meningococcal Infections / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D038542:Neisseria meningitidis, Serogroup C / Q000276:immunology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012698:Serologic Tests / Q000379:methods
D000907:Antibodies, Bacterial; D007075:Immunoglobulin M