ELISA test to detect Chlamydophila pneumoniae IgG

A new ELISA test (Chlamydophila pneumoniae IgG, Vircell, Spain) to detect Chlamydophila pneumoniae IgG was evaluated. The micro-immunofluorescence (MIF) test was used as reference method. Chlamydia trachomatis and Chlamydophila psittaci elementary bodies were also assayed. Two hundred and sixteen sera were included in the study: 66 from patients with peripheral arterial occlusive disease (Panel 1), 68 from adults with pneumonia (Panel 2), 44 from healthy adults (Panel 3) and 38 from patients with a sexuality transmitted disease by C. trachomatis (Panel 4). In Panel 1, 51 sera (77%) had antibody titres between 32 and 128; 4 out of 15 sera with IgG titres < 32 were positive by ELISA test and 2 sera with 32 IgG titres were uncertain by ELISA; the remaining 60 sera were correctly classified, giving a 91% concordance between the techniques. In Panel 2, 55 sera (81%) had IgG titres between 32 and 512; 2 out of 13 sera with IgG titres < 32 were positive by ELISA and 2 sera with 32 titres were uncertain by ELISA; the remaining 64 sera were correctly classified, giving a 97% concordance. In Panel 3, 22 sera (50%) had IgG titres between 32 and 64; only 1 out of 22 sera with IgG titres < 32 was positive by ELISA, giving a 97% concordance between the techniques. In Panel 4, there were 24 (63%) negative, 10 (26%) uncertain and 4 (10%) positive results by ELISA, giving an 86% concordance. The C. pneumoniae ELISA test demonstrated 100% sensitivity and 85% specificity. The IgG ELISA test demonstrated a good concordance with the MIF test without the drawbacks associated with the latter assay. We conclude that the ELISA test could be an alternative to the MIF test.