Infection and venous thrombosis.

Chlamydia pneumoniae infection has been linked to atherosclerosis, but a possible relationship with venous thromboembolism (VTE) had not been sought. We determined circulating anti-C. pneumoniae antibody levels in patients with VTE. 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 Gln or factor II G 20210 A mutations. Other studies did not confirm such an association or found a lower odds ratio. This association remains to be confirmed in other case-control or prospective studies.