Risk of venous thromboembolism in ankylosing spondylitis: a general population-based study.

BACKGROUND

Venous thromboembolism (VTE), including pulmonary embolism (PE) and deep venous thrombosis (DVT), can be life threatening. An increased frequency of VTE has been found in inflammatory conditions. To date, evidence assessing whether this risk is also greater in patients with ankylosing spondylitis (AS) is scarce.

METHODS

Using the provincial British Columbia, Canada healthcare database that encompasses all residents within the province, we conducted matched cohort analyses of incident PE, DVT and overall VTE among incident cases of AS and compared them with individuals randomly selected from the general population without AS. We calculated incidence rates (IRs) of VTE and multivariable analyses after adjusting for traditional risk factors using Cox models.

RESULTS

Among 7190 incident cases of AS, 35 developed PE and 47 developed DVT. IRs of PE, DVT and overall VTE per 1000 person-years for patients with AS were 0.79, 1.06, 1.56 compared with 0.40, 0.50, 0.77 in the control cohort. Corresponding fully adjusted HRs (95% CI) of PE, DVT and VTE were 1.36 (0.92 to 1.99), 1.62 (1.16 to 2.26) and 1.53 (1.16 to 2.01), respectively. The risks of PE, DVT and VTE were highest in the first year of diagnosis with HR (95% CI) of 2.88 (0.87 to 9.62), 2.20 (0.80 to 6.03) and 2.10 (0.88 to 4.99), respectively.

CONCLUSIONS

These findings demonstrate an increased risk of VTE in the general AS population. This risk appears the most prominent in the first year after diagnosis.