Demonstration of an association between Chlamydia pneumoniae infection andvenous thromboembolic disease

Chlamydia pneumoniae infection has been linked to atherosclerosis, but a po ssible relationship with venous thromboembolism (VTE) has not been sought. We determined circulating anti-C. pneumoniae antibody levels in patients wi th 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 Ar g 506 Gln and factor II G 20210 A mutations) were assessed in all the subje cts. Anti-C. pneumoniae IgG antibodies were determined by microimmunofluore scence. All positive plasma samples (titer greater than or equal to 128) we re precisely quantified and tested for the presence of specific IgM antibod ies. 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 odd s 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 2 56, 512 and 1024, respectively. Only one subject (a case patient) with a hi gh IgG titer (greater than or equal to 256) also had specific IgM. High tit ers of anti-C. pneumoniae IgG antibodies are frequently found in patients w ith previous venous thromboembolism. This association deserves to be confir med in other case-control studies anti prospective studies.