Newly diagnosed ankylosing spondylitis (AS) patients are at increased risk for venous thromboembolism (VTE), especially during the first year after diagnosis, according to a population-based study of 7,190 cases.

Dr. J. Antonio Aviña-Zubieta

Dr. J. Antonio Aviña-Zubieta

Previous research has shown an increased risk of VTE, which includes deep vein thrombosis (DVT) and pulmonary embolism (PE), in patients with chronic inflammatory and autoimmune diseases, but the risk for AS patients has not been well studied, wrote J. Antonio Aviña-Zubieta, MD, PhD, of the University of British Columbia in Vancouver and his colleagues.

In a study published in Annals of the Rheumatic Diseases, the researchers identified 7,190 incident cases of AS among adults using a health care database of residents of British Columbia and matched them for age, sex, and entry time into the cohort with 71,900 healthy individuals from the general population over a mean follow-up time of 6.2 years.

The incidence rate of VTE overall per 1,000 person-years was 1.56 among AS patients, compared with 0.77 in a control cohort from the general population. The incidence rates for DVT were 1.06 in AS patients and 0.50 in controls; incidence rates for PE were 0.79 in AS patients and 0.40 in controls.

The adjusted hazard ratios for VTE overall and DVT were similar and statistically significant in AS patients at 1.53 and 1.62, respectively, versus controls. But the adjusted hazard ratio of 1.36 for PE did not reach statistical significance. The adjusted risks of VTE overall, PE, and DVT were highest in the first year of diagnosis, reaching twofold greater risk for all, but none of the risks were statistically significant.

More research is needed to better identify subsets of AS patients at increased risk for VTE, and to assess whether treatment of inflammation can mitigate this risk, but in the meantime clinicians should be alert to the possibility of life-threatening complications from DVT and PE in their AS patients, especially soon after diagnosis, the researchers said.

The findings are supported by the study’s large sample size but are also limited by several factors, including the observational nature of the study and an inability to account for use of NSAIDs, the researchers noted.

“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,” they concluded.

The study was supported in part by grants from the Canadian Arthritis Network, the Arthritis Society of Canada, the British Columbia Lupus Society, and the Canadian Institutes for Health Research. The researchers had no financial conflicts to disclose.

SOURCE: Aviña-Zubieta JA et al. Ann Rheum Dis. 2019 Feb 8. doi: 10.1136/annrheumdis-2018-214388.