AS Patients More Likely to Develop Venous Thromboembolism, Study Says

Patients with ankylosing spondylitis are more likely to develop venous thromboembolism — a condition in which a blood clot that forms in a vein can cause a heart attack or stroke — compared to the general population, a study has found.

The research, “Risk of venous thromboembolism in ankylosing spondylitis: a general population-based study,” was published in the Annals of the Rheumatic Diseases.

Ankylosing spondylitis (AS) is a debilitating type of arthritis that mainly affects the joints of the spine, causing chronic pain and lifelong physical disability.

Although previous studies have suggested that AS patients are more susceptible to heart disease and die prematurely, the incidence of venous thromboembolisms (VTE) and other complications arising from excessive blood clotting, also common in other autoimmune disorders, is still not clear in this patient population.

Now, researchers from the University of British Columbia in Vancouver set out to examine the incidence of VTE in a group of AS patients who had been recently diagnosed, compared to individuals from the general population.

The team gathered clinical data from Canadian residents stored at the Population Data British Columbia (Population Data BC) database.

The incidence of overall VTE, pulmonary embolism (clots that block blood circulation in the lungs), and deep vein thrombosis (clots that block blood circulation in a deep vein, usually in the leg), were assessed in AS patients and compared to individuals without AS randomly selected from the general Canadian population.

From the 7,190 cases of patients who had been diagnosed with AS between January 1996 and December 2012, 35 developed pulmonary embolism, 47 deep vein thrombosis, and 69 VTE. From the 71,900 individuals without AS from the general population, 177 developed pulmonary embolism, 218 deep vein thrombosis, and 336 VTE.

The overall incidence rate of VTE (0.79 vs 0.40), pulmonary embolism (1.06 vs 0.50), and deep vein thrombosis (1.56 vs 0.77) was higher in AS patients compared to individuals randomly selected from the general population.

In addition, AS patients were 1.53, 1.36, and 1.62 times more likely to develop VTE, pulmonary embolism, and deep vein thrombosis than individuals from the general population, respectively.

In AS patients, the risk of developing VTE (2.10 times higher than controls), pulmonary embolism (2.88 times higher than controls) and deep vein thrombosis (2.20 times higher than controls) seemed to be higher in the first year after diagnosis.

“These results call for awareness of this complication, increased vigilance and preventive intervention by controlling the inflammatory process or by anticoagulation in a high-risk AS population,” the researchers said.

“Future investigation should clarify the relative contributions of treatment to the risks of [pulmonary embolism] and [deep vein thrombosis] in AS. Future studies should clarify if certain subsets of the AS population are at higher risk such as those with elevated [C-reactive protein, a protein involved in inflammation], bone marrow edema [fluid buildup in the bone marrow] on MRI, or rapid radiographic progression of spinal fusion. These studies should also assess whether treatment of the inflammatory process can reduce the risk of VTE in AS.”