Thigh lean mass assessment during admission for acute exacerbation of COPD (AECOPD) – a novel DXA scanning protocol

Reduction in thigh muscle size (by ultrasound) predicts readmission following an AECOPD. DXA is the gold standard for lean mass assessment, however dyspnoea prevents some acutely unwell COPD patients tolerating a supine scan. We aimed to determine whether the repeatability of thigh-only scans performed in a seated position is comparable to that from whole-body supine scans. Patients in an observational study were scanned during admission for AECOPD and subsequently at 1, 2 & 3 months in a seated (semi-recumbent) and, where tolerated, supine position. Repeatability was assessed using a generalized linear mixed effects model. 10 participants (3 male) with mean(SD) age 67.7(6.4) years and BMI 27.4(6.8)kg/m² (established on inhaled COPD therapy) were recruited. Median stable eMRC score was 4. Baseline bilateral thigh lean mass was 9072g in the supine and 9207g in the seated scan. No statistically significant difference in repeatability was found between the supine or seated method (R 0.00135, 95%CI 0 to 0.022, p=0.377, Fig 1a) or between time points (R 0, 95%CI 0 to 0.015, p=1, Fig 1b). Significant variance in repeatability between participants was found (R 0.916, 95%CI 0.75 to 0.963, p<0.001, Fig 1c). In this small study thigh lean mass assessed by DEXA in the seated position is repeatable and comparable with DEXA in the supine position. Repeatability varies between individuals for both scan methods. <fig><object-id>erj;64/suppl_68/PA517/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig>