Association of an app-based intervention with improvements in mobility, trunk muscle strength and patient-reported disease activity in axial spondyloarthritis: a 24-week pre-post study.

BACKGROUND

In a nationwide randomised controlled trial among 200 axial spondyloarthritis (axSpA) patients, the medical app Axia improved patient-reported disease activity scores, functional status and quality of life.

OBJECTIVE

This companion study aimed to explore Axia's effects on objective parameters such as mobility, strength and imaging.

DESIGN

Single-centre, two-phase pre-post intervention study over 24 weeks.

METHODS

Thirty-two patients with axSpA on stable pharmacotherapy underwent 12 weeks of standard care (phase I) followed by 12 weeks of Axia use (phase II). The primary endpoint was Bath Ankylosing Spondylitis Metrology Index (BASMI) at week 24 (W24) versus week 12 (W12) and baseline. Secondary endpoints included muscle strength, Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), safety and magnetic resonance imaging (MRI) of the sacroiliac joints.

RESULTS

Twenty-seven (84%) of 32 participants (mean age 49.1 years, 48.1% females and radiographic axSpA, 66.7% biological or targeted synthetic disease-modifying anti-rheumatic drugs therapy) completed the study. During standard care, BASMI (baseline 3.1; W12 3.0; p > 0.05) and BASDAI (baseline 4.7; W12 4.9; p > 0.05) remained unchanged, while median spinal extensor strength declined by 14%. During Axia use, BASMI improved to 2.4 (p < 0.001), BASDAI to 3.7 (p < 0.001) and muscle strength increased by 25% (p < 0.01). BASMI improvement was greater in patients with baseline MRI inflammation. MRI showed no increase or decrease in bone marrow oedema or structural damage. No app-related adverse events occurred.

CONCLUSION

Axia use was associated with improved spinal mobility, extensor strength and disease activity, without relevant safety concerns.

TRIAL REGISTRATION: The study was registered in the German Clinical Trials Register (DRKS00038067).