Venous thromboembolism (VTE) risk was elevated among patients with ankylosing spondylitis, a Canadian population-based study found.
The fully adjusted HR for VTE was 1.53 (95% CI 1.16-2.01) in a large cohort of patients in the province of British Columbia compared with the general population, according to Juan Antonio Aviña-Zubieta, MD, PhD, of the University of British Columbia in Vancouver, and colleagues.
The risk for deep venous thrombosis (DVT) also was significantly elevated in patients with ankylosing spondylitis, with an adjusted HR of 1.62 (95% CI 1.16-2.26). The difference in risk for pulmonary embolism (PE) did not reach statistical significance (HR 1.36, 95% CI 0.92-1.99), the researchers reported online in Annals of the Rheumatic Diseases.
Venous thromboembolism — which includes DVT and PE — is a potentially lethal disorder that has been reported to occur in increased numbers among patients with chronic inflammatory diseases.
Previous studies have demonstrated high rates of cardiovascular disease and mortality among patients with ankylosing spondylitis, but the risks for VTE in this patient group have been less well studied.
To investigate this, the researchers analyzed outcomes from Population Data BC, which contains healthcare service claims and other relevant information for all 4.5 million residents of British Columbia.
During the years 1996 to 2012, there were 7,190 incident cases of ankylosing spondylitis, who were age- and sex-matched with 71,900 controls.
Mean age was 46, and slightly more than half of the cohort were men. Compared with controls, patients had more comorbidities such as hypertension and inflammatory bowel disease, used more medications including glucocorticoids and oral contraceptives, and had more healthcare resource utilization. The analysis adjusted for these between-group differences, the researchers noted.
During a mean of 6.2 years of follow-up, there were:
- For VTE, 69 cases overall in the ankylosing spondylitis group and 336 in the control group, for incidence rates of 1.56 and 0.77 per 1,000 person-years
- For DVT, there were 47 and 218 cases in the ankylosing spondylitis and control groups, respectively, with incidence rates of 1.06/1,000 and 0.50/1,000
- For PE, there were 35 and 177 cases, respectively, with incidence rates of 0.79/1,000 and 0.40/1,000
The researchers also analyzed the impact of ankylosing spondylitis disease duration by calculating hazard ratios for each of the first 5 years after diagnosis, and found the risk to be highest — though not significantly so — in the first year, with 2.10- to 2.88-fold risk of VTE, DVT, and PE.
This lack of significance may reflect inadequate power to detect a rare event such as VTE, the authors suggested.
Previous studies have demonstrated elevated VTE risks in other conditions such as rheumatoid arthritis, systemic sclerosis, and psoriatic arthritis.
“Virchow’s triad of hypercoagulability, endothelial dysfunction, and venous stasis provides a framework for theoretical explanations of this increased risk,” the researchers wrote.
Endothelial dysfunction may play a particularly important role in ankylosing spondylitis patients, who have been shown to have high levels of E-selectin, MCP-1, and soluble vascular adhesion molecule-1.
The thromboembolic risk in AS also may be exacerbated because of a lack of mobility related to pain and spinal fusion.
The results of this study “call for awareness of this complication, increased vigilance, and preventive intervention by controlling the inflammatory process or by anticoagulation in a high-risk ankylosing spondylitis population,” the researchers concluded.
They also called for further research to determine whether improved control of inflammation might decrease the risk for VTE.
A limitation of the study was the reliance on administrative data.
The study was funded by the Canadian Arthritis Network, the Arthritis Society of Canada, the British Columbia Lupus Society, and the Canadian Institutes for Health Research.
The authors reported no financial conflicts.