(CSPOT21) The Risk of Venous Thromboembolism in Two of the Most Common Inflammatory Skin Diseases - a Comparative Cohort Study Consisting of the Adult Populations of Atopic Dermatitis and Psoriasis in the Swedish Specialist Care

Background: Atopic dermatitis (AD) and psoriasis (PsO) are two of the most common inflammatory skin diseases globally, affecting approximately 3-5% and 2-3% respectively, of adults across countries. Patients with inflammatory skin diseases have multiple risk factors for venous thromboembolism (VTE). The risk of VTE in AD and PsO have been studied with conflicting results. With the upcoming introduction of the new drug class Janus kinase (JAK) inhibitors, regulators and healthcare providers have raised a concern that the use of JAK might increase the risk of VTE.

Objectives: To estimate the risk of VTE in patients with AD compared to patients with PsO while taking severity, proxied by treatments, of the diseases into consideration

Methods: Population-based study using Swedish healthcare registers including all patients 18 years of age and older with an AD diagnosis in specialist care between year 2006 and 2022 (index date was the first AD diagnosis during the study period). The reference cohort consisted of patients diagnosed with PsO. Controls from the general population will be added later as an additional reference cohort. For each patient with AD, up to five controls were matched (with replacement) from the PsO cohort by age (±3 years) and sex at index date. Patients in the PsO cohort with a diagnosis of AD before index date were excluded. All patients with a VTE diagnosis before index date were excluded to study only incident VTE events. Patients treated with JAK were excluded from the study. Patients were followed from index date until end of study, death, emigration or outcome, whichever came first.
Incidence rates of VTE per 1000 person-years were calculated for the AD and the PsO cohort. Hazard ratios (HR) with 95% confidence intervals (CI) were calculated from Cox proportional hazard models. Proxies for severity of AD and PsO were constructed by taking treatment into account, where approved conventional systemic treatments for AD and PsO were considered as moderate, while biological treatments were considered as severe. Additional adjustments were made using risk factors for VTE, such as hypertension, stroke, heart failure and diabetes.

Results: We identified 88,857 patients diagnosed with AD were matched to 400,984 patients with PsO. The incidence rate of VTE in the AD cohort was 1.59 (1.51-1.68) per 1000 person-years, compared to 2.19 (2.14-2.24) per 1000 person-years in the PsO cohort. The results from the Cox model indicated a lower risk for VTE in patients with AD compared to patients with PsO; unadjusted HR (95% CI): 0.71 (0.67-0.76) and adjusted HR (95% CI): 0.70 (0.66-0.74).

Conclusions: The VTE risk was lower in patients with AD compared to patients with PsO. With the introduction of JAK inhibitors, it is important to continue monitoring VTE in inflammatory skin diseases.