Qualitative and Quantitative Evaluation of Abdominal Fat and Muscle Tissue Volume in Patients with Ankylosing Spondylitis and Investigation of Their Possible Effects on Biological Agent Treatment Response.

PURPOSE: This study investigates the relationship between sarcopenia index (SMI), quantitative muscle and adipose tissue parameters obtained from abdominal CT, and treatment response to biological agents in patients with ankylosing spondylitis (AS).

MATERIALS AND

METHODS

In this retrospective study, 62 patients (May 2015-May 2024) with an initial diagnosis of AS and available abdominal CT scans at the L2 vertebral level were included. Quantitative parameters including visceral adipose tissue (VAT, cm²), subcutaneous adipose tissue (SAT, cm²), total abdominal muscle area (TAMA), psoas muscle area (PsoA), sarcopenia index (SMI), and tissue attenuation values (HU) were measured. Changes in scores after biological therapy based on the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) were used to assess treatment response. Comparative and correlation analyses were performed between body composition metrics and clinical parameters.

RESULTS

Patients who achieved full recovery exhibited significantly higher TAMA, PsoA, and SMI values compared to those with partial recovery (p < 0.05). These findings suggest that preserved muscle mass and quality are associated with a better response to biological therapy in AS.

CONCLUSION

Opportunistic CT-based body composition analysis provides valuable prognostic information in AS. SMI, TAMA, and psoas muscle volume may serve as potential imaging biomarkers for predicting biological treatment response, supporting personalized management strategies.

KEY POINT: Quantitative assessment of abdominal muscle metrics on routine CT can offer a non-invasive and accessible tool for predicting biological treatment outcomes in ankylosing spondylitis.

KEY POINT: · This is the first study to investigate the association between CT-derived abdominal fat and muscle cross-sectional areas and biologic treatment response in ankylosing spondylitis.. · CT-derived SI, TAMA, and psoas muscle area measurements may serve as adjunct markers alongside clinical parameters in evaluating biologic treatment response.. · CT-detected sarcopenia may be associated with reduced response to biologic therapy in AS patients..

CITATION FORMAT: · Kastan N, Erdem Toslak İ, Yavuz A et al. Qualitative and Quantitative Evaluation of Abdominal Fat and Muscle Tissue Volume in Patients with Ankylosing Spondylitis and Investigation of Their Possible Effects on Biological Agent Treatment Response. Rofo 2026; DOI 10.1055/a-2838-0022.