A new study has determined that a ratio of normal attenuation muscle area (NAMA) to total abdominal muscle area (TAMA) 0.46 or less in patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is independently associated with mortality.
The study, published in the Journal of Rheumatic Diseases, also found that female sex, dyslipidemia, creatinine, and five-factor score were associated with mortality.
“The relationship between sarcopenia and outcomes of patients with autoimmune rheumatic diseases, especially antineutrophil cytoplasmic antibody-associated vasculitis (AAV), has not been well understood,” the authors wrote. “In the present study, we measured NAMA, low attenuation muscle area, and intramuscular adipose tissue in patients with AAV who had undergone CT at disease diagnosis and evaluated the relationship between sarcopenia with comorbidities, clinical manifestations, and patient outcomes.”
The research team retrospectively assessed 136 patients with new-onset AAV who underwent computed tomography (CT) to assess sarcopenia at a single center in Korea between October 2000 and December 2021.
Read more about AAV comorbidities
Additional variables collected included age, sex, body mass index, five-factor score, subtypes of AAV, laboratory results of leukocyte and neutrophil counts, total cholesterol, fasting glucose, creatinine, erythrocyte sedimentation rate, C-reactive protein, aspartate aminotransferase, and alanine aminotransferase.
The results revealed that patients with AAV had higher low attenuation muscle area values and lower NAMA and NAMA/TAMA ratio than healthy individuals, demonstrating the poorer muscle quality in the patients. Specifically, a NAMA/TAMA ratio of 0.46 or less, female sex, dyslipidemia, creatinine, and five-factor score were all independently associated with greater mortality in AAV.
The authors caution that CT imaging is not currently routine in patients with AAV. Given that the results indicate the importance of assessing and monitoring muscle quality in these patients, they suggest grip strength and gait speed could be simple and inexpensive indicators of sarcopenia if the NAMA/TAMA ratio is unavailable.
Reference
Ahn SS, Park YB, Lee SW. Association between computed tomography-assessed sarcopenia and mortality in patients with anti-neutrophil cytoplasmic antibody-associated vasculitis. Int J Rheum Dis. Published online June 23, 2023. doi:10.1111/1756-185X.14795
