Association between computed tomography-assessed sarcopenia and mortality in patients with anti-neutrophil cytoplasmic antibody-associated vasculitis

Aim: Sarcopenia is frequently observed in patients with autoimmune rheumatic diseases; however, its relationship with patient outcomes has not been well understood. This study evaluated the influence of sarcopenia, especially muscle quality, on outcomes of antineutrophil cytoplasmic antibody-associated vasculitis (AAV). Methods: Records of patients with AAV at the Severance Hospital with computed tomography (CT) images taken at initial disease diagnosis were retrospectively reviewed. For measures of sarcopenia, normal attenuation muscle area (NAMA), low attenuation muscle area (LAMA), intramuscular adipose tissue (IMAT), and total abdominal muscle area (TAMA) in the axial muscles of the middle third lumbar vertebra level were calculated. Correlations between NAMA, LAMA, IMAT, and baseline patient characteristics, as well as the association between the NAMA/TAMA ratio and clinical outcomes were assessed. Results: A total of 136 patients with CT images at AAV diagnosis were identified. Correlation analyses revealed that age, female sex, total cholesterol, and alanine aminotransferase were significantly associated with NAMA. LAMA was associated with age, body mass index (BMI), five-factor score (FFS), and C-reactive protein, and a relationship between IMAT and age and BMI was observed. During the follow up of 31.2 months, 23 (16.9%) patients died, and Cox-proportional hazard analysis demonstrated that a NAMA/TAMA <= 0.46 (odds ratio [OR] 10.247, p <.001), female sex (OR 0.206, p =.006), dyslipidemia (OR 3.143, p =.027), creatinine (OR 1.342, p =.012), and FFS (OR 1.775, p =.046), were independently associated with patient mortality. Conclusion: A higher rate of mortality was observed in patients with AAV with NAMA/TAMA <= 0.46, indicating that careful monitoring is required in these patients.