Defining Sarcopenia Using the Third Lumbar Vertebra (L3) Skeletal Muscle Index (L3SMI): Establishing Imaging...

This study aimed to define sarcopenia criteria using the third lumbar vertebra (L3) skeletal muscle index (L3SMI) in Middle Eastern individuals. In a retrospective review, abdominal CT imaging from 200 kidney donors was analyzed. Demographic data, BMI, body surface area, L3 skeletal muscle area (L3SMA), and L3SMI were evaluated. Mean ± SD L3SMA values were 98.63 ± 14.9 cm² for females (n = 48) and 157.52 ± 25.6 cm² for males (n = 152); corresponding L3SMI values were 40.9 ± 5.6 and 55.3 ± 8.8 cm²/m², respectively. Applying Western sarcopenia cutoffs classified 47.9% of females (n = 23/48) and 26.3% of males (n = 40/152) as sarcopenic. Defining cutoffs as two SDs below the mean yielded 29.7 cm²/m² for females and 37.7 cm²/m² for males. These gender-specific cutoffs may aid in the diagnosis of sarcopenia, support clinical risk stratification, and inform future population-based screening strategies in the Middle Eastern region. Larger multiethnic studies are warranted.