Background/Purpose: Risk of venous thromboembolism (VTE) is higher in patients with rheumatoid arthritis (RA) compared to the general population; however whether this risk changes with RA disease duration remains poorly understood. Acknowledging potential heterogeneity in risk by RA duration could support more tailored screening and effective preventive approaches. In a large population based study, we aimed to characterise the RA attributable VTE risk in patients with varying disease durations.

Methods: Adults registered with a general practice from January 1999 to December 2018 were identified from the Royal College of
General Practitioners Research (RCGP) and Surveillance Centre (RSC) primary care database. RA patients (diagnosed prior to and
during the study period), VTE outcome (as a composite of pulmonary embolism [PE] or deep vein thrombosis [DVT]) and individual
PE and DVT outcomes were determined using previously validated algorithms. RA unaffected controls (UCs) were matched 4:1 with
RA patients by current age, sex, calendar time, and years since practice registration using nearest neighbour matching with
replacement. Absolute VTE, PE and DVT rates over 20 years were compared in RA patients versus matched UC across 4 subgroups defined by disease duration (0-2, 2-5, 5-10 and ≥10 years since diagnosis). Across the same subgroups, relative risks over the same period were estimated using Cox proportional hazards models adjusted for sociodemographic and clinical features and established VTE risk factors (body mass index [BMI], smoking status, alcohol use, reduced mobility evidence, thrombophilia, lower limb fracture and family history of VTE).

Results: 117,050 individuals were included: 93,640 UCs and 23,410 RA patients. Of those with RA, 63.9% were included at or within 2 years of diagnosis, 7.8% within 2 to 5 years of diagnosis, 9.8% within 5 to 10 years of diagnosis, and 18.5% > 10 years after diagnosis. Average study follow up for the primary outcome (VTE) was 8.2 years (standard deviation [SD]=6.6 years). RA patients (mean age 59.0, SD 15.5; 28.9% male [n=6776]; mean BMI 27.1, SD 5.6) were similar to matched UCs in clinical characteristics. Unadjusted VTE events rates were consistently higher in RA patients compared to UCs in all subgroups. Relative risk of VTE was similarly increased in RA patients compared to the general population regardless of time since RA diagnosis (adjusted hazard ratios [aHR] range: 1.49-1.63, all p< 0.001). The results obtained when PE (aHR range 1.46-2.02, all p< 0.001) and DVT (aHR range 1.43-1.89, all p< 0.001) were analysed separately were similar to those observed in the composite outcome.

Conclusion: Healthcare professionals should recognize that RA patients face a consistently elevated VTE risk compared to the general population, irrespective of disease duration. This highlights the need for vigilant monitoring and assessment of VTE risk factors even in early stage cases.

This study was sponsored by Pfizer. Momentum Data UK provided project management, medical writing, and statistical support, funded by Pfizer.

This is an encore abstract previously presented/published for the British Society of Rheumatology Annual conference 2024 https://doi.org/10.1093/rheumatology/keae163.094

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/rheumatoid-arthritis-associated-risk-of-venous-thromboembolism-is-not-dependent-on-disease-duration-united-kingdom-based-population-study/