Vainas T, de Graaf R, Stassen FRM, Kurvers HAJM, Grauls GELM, Kitslaar PJEHM, Bruggeman CA. Chlamydia pneumoniae serology: comparing a commercial enzyme immunoassay and microimmunofluorescence test in patients with cardiovascular disease. APMIS 2003;111:363–9. Chlamydia pneumoniae has been associated with cardiovascular disease and the detection of C. pneumoniae antibodies has subsequently challenged many cardiovascular investigators. The micro-immunofluoresence (MIF) test is considered the gold standard for detection of C. pneumoniae antibodies, but requires a high-level of expertise for adequate interpretation. We compared an enzyme immunoassay (EIA) with a microimmunofluorescence test for the detection of C. pneumoniae IgG- and IgA antibodies in sera of 141 patients with atherosclerosis. The MIF test was read by two independent observers. The interobserver agreement of the MIF test for detection of seropositivity at various cut-off levels was good for IgG and for IgA. The intra-test agreement of the EIA was excellent for IgG and IgA. The agreement between EIA and MIF in detection of IgG- and IgA antibodies was adequate at low but not at high titer levels. At low titer levels, the sensitivity, specificity, positive and negative predictive value of EIA compared to the MIF test was sufficient. The sensitivity of the EIA increased, improving the agreement with the MIF at high titer levels by retesting sera with elevated titers at higher pre-dilutions. In conclusion, the EIA shows sufficient agreement with the MIF test in the detection of C. pneumoniae seropositivity. Therefore, the EIA is a practical alternative to the MIF in the detection of C. pneumoniae antibodies in patients with cardiovascular disease, bearing in mind that the sensitivity of the EIA depends on the antibody titer.