Ankylosing Spondylitis Associated With Increased Risk for Venous Thromboembolism

Blood clot. Coloured scanning electron micrograph (SEM) of red blood cells (erythrocytes, red) clumped together with fibrin (brown) to form a blood clot. Magnification: x5000 when printed 10 centimetres wide.
Data show an increased risk for deep vein thrombosis and venous thromboembolism in patients with ankylosing spondylitis.

Study data published in Annals of the Rheumatic Diseases demonstrate an increased risk for deep vein thrombosis (DVT) and venous thromboembolism (VTE) in patients with ankylosing spondylitis (AS). 

Using the provincial British Columbia healthcare database, investigators conducted matched cohort analyses of incident pulmonary embolism (PE), DVT, and VTE among patients with AS compared with the general population. The database comprises all provincially funded healthcare services data since 1990 for residents of British Columbia, Canada, including outpatient medical visits, hospital admissions and discharges, demographic data, and dispensed prescription medications. 

The incident AS cohort included individuals first diagnosed between January 1996 and December 2012. Incident AS and VTE were identified using International Classification of Diseases 9th edition Clinical Modification and 10th edition Clinical Modification codes. Cox proportional hazard regression models were used to assess risk for PE, DVT, and both outcomes combined among patients with AS.  

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The final cohort included 7190 patients with incident AS and 71,900 comparison cases matched by age, sex, and study entry time. Compared with the comparison cohort, patients with AS had more comorbidities at baseline, higher use of medications, higher hospital resource utilization, and higher Charlson Comorbidity Index scores. 

Patients with AS had greater incidence rates per 1000 person-years of PE, DVT, and VTE (0.79, 1.06, and 1.56, respectively) compared with controls (0.40, 0.50, and 0.77, respectively). The adjusted hazard ratios (HRs) for PE, DVT, and VTE were greatest in the first year following diagnosis, at 2.88 (95% CI, 0.87-9.62), 2.20 (95% CI, 0.80-6.03), and 2.10 (95% CI, 0.88-4.99), respectively. 

When the entire follow-up period was assessed, only the risks for DVT (HR, 1.62; 95% CI, 1.16-2.26) and VTE (HR, 1.53; 95% CI, 1.16-2.01) were significantly elevated compared with controls.  

These results demonstrate an elevated risk for VTE, including DVT, among patients with AS. As potentially life-threatening complications, clinicians should be aware of the risk for these complications in patients. Future studies are needed to identify which patients with AS are at particularly high risk.  


Aviña-Zubieta JA, Chan J, De Vera M, Sayre EC, Choi H, Esdaile J. Risk of venous thromboembolism in ankylosing spondylitis: a general population-based study [published online February 8, 2019]. Ann Rheum Dis. doi:10.1136/annrheumdis-2018-214388