A novel IMU-based clinical assessment protocol for Axial Spondyloarthritis: a protocol validation study.

Clinical assessment of spinal impairment in Axial Spondyloarthritis is currently performed using the Bath Ankylosing Spondylitis Metrological Index (BASMI). Despite being appreciated for its simplicity, the BASMI index lacks sensitivity and specificity of spinal changes, demonstrating poor association with radiographical range of motion (ROM). Inertial measurement units (IMUs) have shown promising results as a cost-effective method to quantitatively examine movement of the human body, however errors due to sensor angular drift have limited their application to a clinical space. Therefore, this article presents a wearable sensor protocol that facilitates unrestrained orientation measurements in space while limiting sensor angular drift through a novel constraint-based approach. Eleven healthy male participants performed five BASMI-inspired functional movements where spinal ROM and continuous kinematics were calculated for five spine segments and four spinal joint levels (lumbar, lower thoracic, upper thoracic and cervical). A Bland-Altman analysis was used to assess the level of agreement on range of motion measurements, whilst intraclass correlation coefficient (ICC), standardised error measurement, and minimum detectable change (MDC) to assess relative and absolute reliability. Continuous kinematics error was investigated through root mean square error (RMSE), maximum absolute error (MAE) and Spearman correlation coefficient (ρ). The overall error in the measurement of continuous kinematic measures was low in both the sagittal (RMSE = 2.1°), and frontal plane (RMSE = 2.3°). ROM limits of agreement (LoA) and minimum detectable change were excellent for the sagittal plane (maximum value LoA 1.9° and MDC 2.4°) and fair for lateral flexion (overall value LoA 4.8° and MDC 5.7°). The reliability analysis showed excellent level of agreement (ICC > 0.9) for both segment and joint ROM across all movements. The results from this study demonstrated better or equivalent accuracy than previous studies and were considered acceptable for application in a clinical setting. The protocol has shown to be a valuable tool for the assessment of spinal ROM and kinematics, but a clinical validation study on Axial Spondyloarthritis patients is required for the development and testing of a novel mobility index.

Should axial spondyloarthritis without radiographic changes be treated with anti-TNF agents?

A spectrum of disease extends beyond the rigid confines of ankylosing spondylitis (AS). Axial spondyloarthritis (axSpA) encompasses non-radiographic axSpA (nr-axSpA) in individuals without established radiographic changes but with other clinical/imaging axSpA features and AS in those with definite sacroiliac joint changes on pelvic X-rays. A broad consensus about the management of nr-axSpA is emerging among clinicians, but the evidence base remains open to question. To explore whether nr-axSpA and AS should be treated similarly, we examined the literature on their prevalence, natural history, disease burden, and treatment. There is strong evidence that nr-axSpA and AS are expressions of the same disease. Approximately 10% of patients with nr-axSpA will develop radiographic disease over 2 years; after >20 years, the figure may exceed 80%. Nr-axSpA patients have lower CRP and less spinal inflammation on MRI than AS patients but similar disease activity, pain, and quality-of-life impairment. Most patients with nr-axSpA manage well with conservative treatment, but a minority has severe disabling symptoms. Anti-TNF therapy has demonstrated similar efficacy and safety in nr-axSpA and AS. Current evidence does not clearly indicate that anti-TNF treatment can inhibit or limit bony progression of AS, the basis of conservative and anti-TNF treatment is control of symptoms and function. For some patients with nr-axSpA, the need for powerful treatments is as great as in some with AS; thus, treatment of axSpA should be consistent across the axSpA spectrum with anti-TNF agents being available, irrespective of radiographic change, according to the same criteria as those applied to AS.

The assessment of ankylosing spondylitis in clinical practice.

Ankylosing Spondylitis (AS) is a chronic inflammatory arthritis that predominantly affects the axial skeleton in adolescent patients causing spinal pain and stiffness. There is a marked delay, on average 8 years, between onset of disease symptoms and clinical diagnosis. The distinction between the symptoms of mechanical and inflammatory back pain remains one of the main contributing factors for the delay in diagnosis. Several classification criteria exist to aid the diagnosis of AS, but their accuracy is poor. The Ankylosing Spondylitis Assessment Study group (ASAS) has defined a core set of domains for clinical outcome measurement in AS in order to assess the disease process in individual patients and to identify those with rapidly progressive disease. New therapies, such as the tumor necrosis factor (TNF) inhibitors, have transformed the treatment paradigm in AS, especially for those patients with aggressive disease. Thus, the definition of both patient selection criteria for these agents and the development of clinical methods to assess response to therapy have become a priority. This Review focuses on measuring the degree of disease activity, function and damage in patients with AS in an ambulatory care setting, and the assessment of suitability of various outcome measures for monitoring response to treatment with TNF inhibitors.