Assessing the health burden of a rare, multisystem autoimmune disease: An epidemiological analysis of comorbidities in ANCA-associated vasculitis

Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) encompasses a heterogeneous group of rare, multisystem autoimmune disorders. Improved treatment regimens have increased patient longevity and inevitably shifted the burden experienced by AAV patients. Comorbidities are increasingly identified as drivers of premature mortality and increased health burden in AAV patients. However, studies on comorbidities in AAV are confined to secondary analysis of clinical trial data and small studies from tertiary care centres. There is a need for comprehensive population-based assessment of comorbidities in AAV patients to attain a clear understanding of the true health burden of AAV. This study aims to (i)contextualise comorbidities in AAV patients by comparing the prevalence of comorbidities in AAV patients to a reference population, and (ii)explore potential risk factors associated with the most common comorbidities. The Primary Care Clinical Informatics Unit (PCCIU) database provides a representative sample of patients from participating Scottish general practices. Read codes were used to identify AAV patients (n: 360, 50.3% male) and five corresponding age- (± 5 years), sex- and general practice-matched controls for each AAV patient. Data on demographics, selected common comorbidities and medications were retrieved for each participant. Descriptive statistics will be used to describe the study participants according to AAV type, demographics and comorbidities. Conditional logistic regression will be carried out to quantify differences between AAV patients and general population controls. Cox proportional hazard regression models, if applicable, will be conducted to identify potentially modifiable risk factors for comorbidities. The data is in the analysis stage, and future plans include conducting a comprehensive data linkage of a population-based AAV cohort with Scottish national databases which would enable robust assessment of comorbidities in AAV. It is anticipated that the results of this study would provide a greater understanding of the evolving health burden of AAV, and may subsequently inform clinical decision-making.