Usefulness and limitations of single-slice computed tomography analysis at the third lumbar region in the assessment of sarcopenia

In the previous issue of Critical Care, Moisey and colleagues [1] report that sarcopenia has potential to serve as a predictor for mortality, discharge disposition, and ICU utilization. Sarcopenia may be mitigated by adequate nutrition supply and early rehabilitation, and so identification of patients with ICU-acquired weakness, who could benefit from rehabilitation, is of fundamental importance [2].

Sarcopenia diagnosis is based on estimation of muscle mass. Whole-body imaging methods like computed tomography (CT) and magnetic resonance imaging (MRI) can precisely measure muscle mass, but limitations of these modalities led to new tools for daily practice. The European Working Group on Sarcopenia in Older People (EWGSOP) recommends the use of dual-energy x-ray absorptiometry (DXA) as an alternative [3]. Nowadays, single-slice CT image analysis, which was used in the study by Moisey and colleagues, is becoming a popular alternative. Validation of this technique was previously assessed by comparing the single-slice CT analysis at the third lumbar (L3) region with DXA, which is not the gold standard [4]. Measurement errors related to DXA might affect these validation results. Although Shen and colleagues [5] compared single-slice CT analysis and whole-body MRI, they reported results for the fourth-fifth lumbar region, not for the L3 region. Moreover, this study was conducted among healthy subjects and this limited the generalization of results for the ICU setting.

The EWGSOP recommends the measurement of muscle power, function, and mass for a sarcopenia diagnosis [3]. As muscle function and power data of patients were not reported in the present article, we do not know whether all participants were accurately classified as sarcopenic.