Demonstration of an association between Chlamydia pneumoniae infection and venous thromboembolic disease

Chlamydia pneumoniae infection has been linked to atherosclerosis, but a possible relationship with venous thromboembolism (VTE) has not been sought. We determined circulating anti-C. pneumoniae antibody levels in patients with VTE. We studied 176 case patients with objectively diagnosed VTE and 197 age- and sex-matched healthy controls, in a retrospective study. Acquired risk factors for VTE and frequent predisposing genetic factors (factor V Arg 506 Gln and factor II G 20210 A mutations) were assessed in all the subjects. Anti-C. pneumoniae IgG antibodies were determined by microimmunofluorescence. All positive plasma samples (titer greater than or equal to 128) were precisely quantified and tested for the presence of specific IgM antibodies. Fifty-four percent of the cases and 15.9% of the controls had specific IgG titers of at least 256 (p <0.0001). The crude odds ratio for VTE was 6.2 (95% CI, 3.8-10.1), and rose to 7.7 (4.5-13.2) after excluding subjects carrying the factor V Arg 506 Gin or factor II G 20210 A mutations. The odds ratio for VTE increased with the Ige titer: the adjusted odds ratios were 2.1 (95% CI, 1.1-4.1), 5.3 (2.7-10.6) and 33.0 (4.4-248.4) for titers of 256, 512 and 1024, respectively. Only one subject (a case patient) with a high IgG titer (greater than or equal to 256) also had specific IgM. High titers of anti-C. pneumoniae IgG antibodies are frequently found in patients with previous venous thromboembolism. This association deserves to be confirmed in other case-control studies anti prospective studies.