An Increased Risk for Blood Clots in Ankylosing Spondylitis

Research links ankylosing spondylitis to an increased risk for venous thromboembolism and deep vein thrombosis. (©Henadzy_AdobeStock)

A recent study published in the Annals of the Rheumatic Diseases shows that ankylosing spondylitis is linked to an increased risk for venous thromboembolism and deep vein thrombosis.

Prior research has suggested an increased risk for venous thromboembolism in patients with chronic inflammatory and autoimmune diseases. However, limited evidence exists on the risk for venous thromboembolism―as well as deep vein thrombosis and pulmonary embolism―in patients with ankylosing spondylitis. One Swedish population-based study found a 50 percent increase in the risk of venous thromboembolism n patients with ankylosing spondylitis when compared to the general population.

THE STUDY

Researchers, led by Juan Antonio Aviña-Zubieta, M.D., Ph.D., of the University of British Columbia in Vancouver, base the study on data from a Canadian healthcare database. A matched cohort analysis of incident pulmonary embolism, deep vein thrombosis and both outcomes combined was performed among incident cases of ankylosing spondylitis and with matched general population subjects.

The incident ankylosing spondylitis cohort included individuals diagnosed for the first time between January 1996 and December 2012 with no previous recorded history or diagnosis of ankylosing spondylitis in the preceding six years.

Incident venous thromboembolism cases were determined from patient records and relevant covariates were recorded. Incidence rates of venous thromboembolism were calculated and subjected to multivariable analyses after adjusting for traditional risk factors using Cox models.

Among 7,190 incident cases of ankylosing spondylitis, 35 developed pulmonary embolism and 47 developed deep vein thrombosis. The incident rate per 1,000 person-years was higher in the ankylosing spondylitis cohort for pulmonary embolism, deep vein thrombosis and venous thromboembolism (0.79, 1.06, 1.56, respectively) compared with the comparison cohort (0.40, 0.50, 0.77, respectively).

Although not statistically significant, the adjusted risks of pulmonary embolism, deep vein thrombosis and venous thromboembolism were highest in the first year after diagnosis with a greater than two-fold increased risk. At the end of the follow-up period risks for deep vein thrombosis and venous thromboembolism were significantly increased whereas the risk of pulmonary embolism was not.

TAKE-HOME POINTS

Ankylosing spondylitis is associated with an increased risk of venous thromboembolism. Overall, there appeared to be a 50 percent increase in risk of venous thromboembolism with a larger effect seen in deep vein thrombosis than in pulmonary embolism.

Dr. Juan Avina-Zubieta and colleagues wrote, “we demonstrated a 53 percent and 63 percent increased risk of venous thromboembolism and deep vein thrombosis, respectively. The risk of pulmonary embolism was increased by 36 percent, but this was not statistically significant.”


Clinicians should be particularly vigilant in the first year after ankylosing spondylitis diagnosis since there was a trend toward higher risk for venous thromboembolism during that time. Patients should be educated about this potential risk for blood clots.

Because venous thromboembolism and in particular, pulmonary embolus are so serious and often life threatening more research is needed to see if traditional preventative measures should be taken in patients with ankylosing spondylitis. Often patients who are at high risk for blood clots are put on blood thinning anticoagulant medications with the goal of preventing catastrophe.

Anticoagulant medications themselves are not without risk, so it is imperative that more evidence be produced before preventative treatment is recommended in patients with ankylosing spondylitis but no other risk factors for venous thromboembolism. Venous thromboembolism risk can be added to the already significant cardiovascular risk normally assigned to rheumatic disease and further underscores the dramatic impact of inflammation on the cardiovascular system apart from the skeletal manifestations.

The authors call for awareness of this serious complication and vigilance coupled with preventive intervention in the form of tight control of disease activity. These recommendations are in line with treat-to-target principles already in practice and endorsed by EULAR and the American College of Rheumatology.

While it is unknown if tight control of disease activity in ankylosing spondylitis will reduce the risk of venous thromboembolism, it is a worthwhile goal in and of itself and will lead to more research into it’s ability to mitigate the risk of venous thromboembolism in this patient population.

ABOUT THE AUTHOR

Gregory M. Weiss, M.D., is a cardiothoracic anesthesiologist practicing in Virginia. He is a frequent contributor to Rheumatology Network.

REFERENCE
Aviña-Zubieta JA, Chan J, De Vera M, et al. Risk of venous thromboembolism in ankylosing spondylitis: a general population-based study. Annals of the Rheumatic Diseases. Published Online First: 08 February 2019. doi: 10.1136/annrheumdis-2018-214388