POS0964 CHARACTERISTICS AND BURDEN OF DISEASE IN PATIENTS WITH RADIOGRAPHIC VERSUS NON-RADIOGRAPHIC AXIAL SPONDYLOARTHRITIS IN THE ANKYLOSING SPONDYLITIS REGISTRY OF IRELAND COHORT

Abstract

Background:Axial spondyloarthritis (axSpA) is an umbrella term for types of inflammatory arthritis that primarily affect the spine and the sacroiliac joints. It is comprised of patients with both radiographic (r-axSpA) and non-radiographic features (nr-axSpA). R-axSpA was historically known as Ankylosing Spondylitis. Previous studies have shown the burden of disease to be largely similar in patients with radiographic versus non-radiographic axial spondyloarthritis in cohorts both in the US and Europe [1]. The Ankylosing Spondylitis Registry of Ireland (ASRI) was formed with the objective to measure the burden of axial spondyloarthritis in the population and identify early predictors of a poor outcome. All patients in the registry are 18 years or older and meet Assessment of Spondyloarthritis International Society (ASAS) criteria for a diagnosis of SpA.Objectives:To compare the characteristics and burden of disease in patients with radiographic versus non-radiographic axial spondyloarthritis in the ASRI cohort.Methods:Patients with radiographic axial spondyloarthritis (r-axSpA) were defined as those with x-ray evidence of sacroiliitis. Patients with non-radiographic axial spondyloarthritis (nr-axSpA) were defined as having MRI evidence of sacroiliitis but no x-ray evidence of sacroiliitis. A standardised clinical assessment was performed on each patient and structured interviews provided patient-reported data. For each patient the following scores were captured: Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI), Bath Ankylosing Spondylitis Metrology Index (BASMI), Health Assessment Questionnaire (HAQ) assesses the self-reported functional status for performing activities of daily living, and the Ankylosing Spondylitis Quality of Life (ASQoL) questionnaire. Categorical variables were summarized as percentages with frequency counts, and continuous variables with a mean and standard deviation. Statistical comparisons between subgroups were evaluated using 2 sample t-tests for continuous variables and chi-square tests for categorical variables.Results:764 patients were available for analysis. Analysis of radiographic status showed 88.1% (n=673) of patients with r-axSpA and 11.9% (n=91) with nr-axSpA. Patients with nr-axSpA were younger (41.3 vs. 46.6 years, p<0.01), had shorter disease duration (14.8 vs. 20.2 years, p<0.01), lower proportion of males (66.6% vs. 78.4%, p=0.02) with lower rates of HLA-B27 positivity (73.6% vs. 90.5%, p<0.01). The nr-axSpA group had lower BASDAI (3.37 vs. 4.05, p=0.01), BASFI (2.46 vs. 3.88, p<0.01), BASMI (2.33 vs. 4.34, p<0.01), ASQoL (5.2 vs. 6.67, p=0.02), and HAQ scores (0.38 vs. 0.57, p<0.01). There were no significant differences in the prevalence of extra-articular manifestations.Conclusion:This study provides evidence that the burden of disease is less in patients with non-radiographic axial spondyloarthritis than radiographic axial spondyloarthritis, as demonstrated by better BASDAI, BASFI, BASMI, HAQ and ASQoL scores.