High Reproducibility of an Automated Measurement of Mobility for Patients with Axial Spondyloarthritis

Validity and feasibility of remote measurement systems for functional movement and posture assessments in people with axial spondylarthritis

INTRODUCTION

This study aimed to estimate the criterion validity of functional movement and posture measurement using remote technology systems in people with and without Axial spondylarthritis (axSpA).

METHODS

Validity and agreement of the remote-technology measurement of functional movement and posture were tested cross-sectionally and compared to a standard clinical measurement by a physiotherapist. The feasibility of remote implementation was tested in a home environment. There were two cohorts of participants: people with axSpA and people without longstanding back pain. In addition, a cost-consequence analysis was performed.

RESULTS

Sixty-two participants (31 with axSPA, 53% female, age = 45(SD14), BMI = 26.6(SD4.6) completed the study. In the axSpA group, cervical rotation, lumbar flexion, lumbar side flexion, shoulder flexion, hip abduction, tragus-to-wall and thoracic kyphosis showed a significant moderate to strong correlation; in the non-back pain group, the same measures showed significant correlation ranging from weak to strong.

CONCLUSIONS

Although not valid for clinical use in its current form, the remote technologies demonstrated moderate to strong correlation and agreement in most functional and postural tests measured in people with AxSA. Testing the CV-aided system in a home environment suggests it is a safe and feasible method. Yet, validity testing in this environment still needs to be performed.

Test-retest reliability of outcome measures: data from three trials in radiographic and non-radiographic axial spondyloarthritis

Objectives

Aim of this study was to assess test–retest reliability of candidate instruments for the mandatory domains of the Assessment of Spondyloarthritis international Society (ASAS)-Outcome Measures in Rheumatology core set for axial spondyloarthritis (axSpA).

Methods

Screening and baseline data from COAST-V, COAST-X and RAPID-axSpA was used to evaluate test–retest reliability of each candidate instrument for the mandatory domains (disease activity, pain, morning stiffness, fatigue, physical function, overall functioning and health). A maximum time interval of 28 days between both visits was used for inclusion in this study. Test–retest reliability was assessed by intraclass correlation coefficient (ICC). Bland and Altman plots provided mean difference and 95% limits of agreement, which were used to calculate the smallest detectable change (SDC). Data were analysed for radiographic and non-radiographic axSpA separately.

Results

Good reliability was found for Ankylosing Spondylitis Disease Activity Score (ICC 0.79, SDC 0.6), C reactive protein (ICC 0.72–0.79, SDC 12.3–17.0), Bath Ankylosing Spondylitis Functional Index (ICC 0.87, SDC 1.1) and 36-item Short-Form Health Survey (ICC Physical Component Summary 0.81, SDC 4.7, Mental Component Summary 0.80, SDC 7.3). Moderate reliability was found for Bath Ankylosing Spondylitis Disease Activity Index (ICC 0.72, SDC 1.1), patient global assessment (ICC 0.58, SDC 1.5), total back pain (ICC 0.64, SDC 1.3), back pain at night (ICC 0.67, SDC 1.3), morning stiffness (ICC 0.52–0.63, SDC 1.5–2.2), fatigue (ICC 0.65, SDC 1.3) and ASAS-Health Index (ICC 0.74, SDC 2.5). Reliability and SDC for the radiographic and non-radiographic axSpA subgroups were similar.

Conclusion

Overall reliability was good, and comparable levels of reliability were found for patients with radiographic and non-radiographic axSpA, even though most instruments were developed for radiographic axSpA. Composite measures showed higher reliability than single-item measures in assessing disease activity in patients with axSpA.

Prevalence and Associated Factors of Low Bone Mineral Density in the Femoral Neck and Total Hip in Axial Spondyloarthritis: Data from the CASTRO Cohort

Studies on osteoporosis in axial spondyloarthritis (axSpA) have focused on the lumbar segment, and few studies have assessed bone mineral density (BMD) in the hip and femoral neck in these patients. The aim of this study was to evaluate the prevalence of low BMD and osteopenia in the total hip or femoral neck and the factors associated with these conditions in axSpA patients. This was a single-centre, observational, cross-sectional study among consecutive patients with axSpA according to the ASAS criteria from the CASTRO registry. All patients underwent total hip and femoral neck DXA BMD measurements. Low BMD was defined as a Z-score less than −1, and osteopenia was defined as a T-score less than −1. Multivariate logistic and generalised linear regressions were used to evaluate factors independently associated with low BMD and osteopenia in the hip or femoral neck and those associated with variability in BMD, respectively. A total of 117 patients were included, among which 30.8% were female and the mean age was 45 years. A total of 36.0% of patients had low BMD (28.1% in the total hip and 27.4% in the femoral neck), and 56.0% of patients had osteopenia (44.7% in the total hip and 53.8% in the femoral neck). A multivariate logistic regression showed that age, radiographic sacroiliitis and ASAS-HI were independently associated with low BMD in the total hip or femoral neck. Factors that were independently associated with osteopenia were Body Mass Index, disease duration, radiographic sacroiliitis and ASAS-HI. In conclusion, 36% of the patients with axSpA had low BMD in the total hip or femoral neck. A younger age and radiographic sacroiliitis were the most important factors associated with decreased BMD.

Validity and reliability of a sensor-based electronic spinal mobility index for axial spondyloarthritis

OBJECTIVE

To evaluate the validity and reliability of inertial measurement unit (IMU) sensors in the assessment of spinal mobility in axial spondyloarthritis (axSpA).

METHODS

A repeated measures study design involving 40 participants with axSpA was used. Pairs of IMU sensors were used to measure the maximum range of movement at the cervical (Cx) and lumbar (Lu) spine. A composite IMU score was defined by combining the IMU measures. Conventional metrology and physical function assessment were performed. Validation was assessed considering the agreement of IMU measures with conventional metrology and correlation with physical function. Reliability was assessed using intra-class correlation coefficients (ICCs).

RESULTS

The composite IMU score correlated closely (r = 0.88) with the BASMI. Conventional Cx rotation and lateral flexion tests correlated closely with IMU equivalents (r = 0.85, 0.84). All IMU movement tests correlated strongly with BASFI, while this was true for only some of the BASMI tests. The reliability of both conventional and IMU tests (except for chest expansion) ranged from good to excellent. Test-retest ICCs for individual conventional tests varied between 0.57 and 0.91, in comparison to a range from 0.74 to 0.98 for each of the IMU tests. Each of the composite regional IMU scores had excellent test-retest reliability (ICCs=0.94-0.97), comparable to the reliability of the BASMI (ICC=0.96).

CONCLUSION

Cx and Lu spinal mobility measured using wearable IMU sensors is a valid and reliable assessment in multiple planes (including rotation), in patients with a wide range of axSpA severity.

Measuring Spinal Mobility Using an Inertial Measurement Unit System: A Validation Study in Axial Spondyloarthritis

Portable inertial measurement units (IMUs) are beginning to be used in human motion analysis. These devices can be useful for the evaluation of spinal mobility in individuals with axial spondyloarthritis (axSpA). The objectives of this study were to assess (a) concurrent criterion validity in individuals with axSpA by comparing spinal mobility measured by an IMU sensor-based system vs. optical motion capture as the reference standard; (b) discriminant validity comparing mobility with healthy volunteers; (c) construct validity by comparing mobility results with relevant outcome measures. A total of 70 participants with axSpA and 20 healthy controls were included. Individuals with axSpA completed function and activity questionnaires, and their mobility was measured using conventional metrology for axSpA, an optical motion capture system, and an IMU sensor-based system. The UCOASMI, a metrology index based on measures obtained by motion capture, and the IUCOASMI, the same index using IMU measures, were also calculated. Descriptive and inferential analyses were conducted to show the relationships between outcome measures. There was excellent agreement (ICC > 0.90) between both systems and a significant correlation between the IUCOASMI and conventional metrology (r = 0.91), activity (r = 0.40), function (r = 0.62), quality of life (r = 0.55) and structural change (r = 0.76). This study demonstrates the validity of an IMU system to evaluate spinal mobility in axSpA. These systems are more feasible than optical motion capture systems, and they could be useful in clinical practice.

Measuring spinal mobility in early axial spondyloarthritis: does it matter?

OBJECTIVES

To investigate the frequency and order of impairment of spinal mobility measures (SMMs) and their cross-sectional and longitudinal usefulness in early axial spondyloarthritis.

METHODS

SMMs measurements of patients from the DESIR (5-year data) and SPACE (2.6 (1.9) years of follow-up) cohorts were analysed. Cross-sectional (group level) and longitudinal (individual level) analyses were performed comparing SMMs to pre-defined cut-offs derived from healthy individuals. Subgroup analyses were used to study patient and disease characteristics potentially influencing spinal mobility. Reliability was analysed using intraclass correlation coefficients and the smallest detectable change.

RESULTS

In 328 DESIR and 148 SPACE patients, lateral spinal flexion (LSF) and mSchober were the most impaired SMMs. If both (LSF and mSchober) were measured, 84% (DESIR) and 74% (SPACE) of the patients with impairment in ≥1 SMM would be captured. LSF and Bath AS Metrology Index best discriminated between subgroups of patients (higher impairment in patients ever treated with biologics, with higher disease activity and presence of baseline syndesmophytes): e.g. 31% of LSF impairment in patients with Ankylosing Spondylitis Disease Activity Score (ASDAS) < 2.1 in ≥2/3 visits vs 49% in those with ASDS ≥ 2.1. A high variability in SMMs within the same patient over time was observed, even when restricting the analysis to patients with low disease activity. Reliability of SMMs was 'fair' to 'good' (inter-reader intraclass correlation coefficients (2, 1): 0.55-0.84; intrareader intraclass correlation coefficients (2, 1): 0.49-0.72). Smallest detectable changes were in general high, e.g. 5.1 cm for LSF.

CONCLUSION

Cross-sectional use of SMMs, at the group level, is informative in patients with early axial spondyloarthritis. However, the high variation of SMMs over time impairs their use, at the individual patient level.