Chlamydia pneumoniae IgA‐ and IgG antibodies in young survivors of myocardial infarction. A comparison of antibody detection by a microimmunofluorescence test and an enzyme immunoassay

. Halvorsen DS, Børvik T, Njølstad I, Gutteberg TJ, Vorland LH, Hansen J‐B (University Hospital of Tromsø; and Institute of Community Medicine, Tromsø, Norway). Chlamydia pneumoniae IgA‐ and IgG antibodies in young survivors of myocardial infarction. A comparison of antibody detection by a microimmunofluorescence (MIF) test and an enzyme immunoassay (EIA). J Intern Med 2002; 251: 142–147. Objectives. Chronic Chlamydia pneumoniae infection is considered as a cardiovascular risk factor and antibodies are commonly analysed by the subjective microimmunofluorescence (MIF) test. We wanted to investigate the C. pneumoniae IgA‐ and IgG seroprevalence in young survivors of myocardial infarction and matched controls, and to compare the agreement of detecting antibodies between a MIF test and an enzyme immunoassay (EIA). Design. A total of 61 patients hospitalized as a result of myocardial infarction, 51 patients hospitalized with chest pain and negative exercise‐ECG and 61 age and sex matched controls (mean age 53.3 years, range 40–60 years) were included in this case–control study. Serological comparisons were expressed as sensitivity, specificity and interrater agreement (K or Kw) of the EIA test related to the MIF test. Results. Presence of IgA (cut off=16) antibodies was significantly higher in coronary heart patients compared with controls for both assays (P=0.02 by the MIF and P=0.05 by the EIA test). The presence of IgG (cut off=32) antibodies was significantly higher amongst patients (P=0.05) when analysed by the MIF‐test, but not with the EIA‐test (P=0.16). The strength of agreement between the assays was good for both IgA‐ (Kw=0.67) and IgG (Kw=0.79) analyses. However, only 52.8% of the IgA samples classified as strong positive (cut‐off=32) by the MIF test were strong positive by the EIA test (K=0.56). Only 73.2% of the negative IgG samples (