Clinical aspects of axial spondyloarthritis : improving disease outcome

Abstract

Axial spondyloarthritis (SpA) is a spectrum of diseases with characteristic spinal and sacroiliac (SI) joint inflammation leading to syndesmophyte formation and ankylosis. It consists of ankylosing spondylitis (AS), psoriatic arthritis (PsA), reactive arthritis (ReA), inflammatory bowel disease (IBD) associated spondyloarthritis, and undifferentiated spondyloarthritis (uSpA). With onset predominantly in young adulthood, it has significant impact on physical, social, psychological, and social functioning Pharmacological treatment of SpA includes non-steroidal anti-inflammatory drugs (NSAID), conventional synthetic disease modifying anti-rheumatic drugs (csDMARD), and biological disease modifying anti-rheumatic drugs (bDMARD).

The aim of this thesis was improving clinical outcome of axial SpA, divided in to three parts. Part I was related to comorbidities, and associations with pharmacological treatments. Prospective data on participants with axial SpA had the following investigations done: whole spine and sacroiliac (SI) joint magnetic resonance imaging (MRI), radiographs, echocardiograms, carotid doppler, blood investigations, and expert-diagosed depression. It showed that axial SpA was associated with increased carotid intima-media thickness, worsened diastolic function, and depression.

Data on more than 2500 patients with SpA with an average follow-up period of more than 10 years captured on a centralised medical record were analysed. Compared to patients with non-specific back pain (NSBP), patients with SpA were found to have increased risk of community acquired pneumonia requiring hospitalization. Infliximab, smoking, and long term steroid therapy were the associated risk factors. Risk of cutaneous herpes zoster (HZ) in SpA was not less than in rheumatoid arthritis (RA). Risk of development and progression of cervical neoplasia was low with conventional and biological DMARDs.

Part II investigated the use of conventional MRI sequences in axial SpA. Clinical significance of various lesions, including fatty corner lesions (FCL), and costovertebral and facet joint lesions, on short tau inversion recovery (STIR) sequence was explored. Thoracic FCL could be used for diagnosis and costovertebral and facet joint lesions were associated with limited spinal movements and impaired functional status.

Part III explored the innovative use of diffusion weighted imaging (DWI) for monitoring of axial disease activity. Although DWI was found to have no addition value in diagnosis, its derived apparent diffusion coefficient (ADC), by quantifying the intensity of inflammation, correlated well with clinical disease activity scores. The new MRI sequence could be an imaging biomarker for axial SpA.