Assessing sarcopenia: The JOHAS (Judgment of Objective Hyper-steatosis and Atrophy in Sarcopenia) index as a pragmatic surrogate for skeletal muscle index by bioimpedance analysis.

The aim of this study was to develop a new, less cumbersome index for determining sarcopenia using axial slice images from computed tomography (CT) as a surrogate for the skeletal muscle index (SMI) measured by bioelectrical impedance analysis (BIA). We devised the JOHAS index (Judgment of Objective Hyper-steatosis and Atrophy in Sarcopenia), calculated from the measurements of the iliopsoas and erector spinae muscles in the axial CT slices at the L4 lumbar vertebral level.

The JOHAS index is defined as: JOHAS index = ∑ [(cross-sectional area of each muscle [cm]/patient height [cm]) × (CT number + 108)], where ∑ is defined as the sum of the values in the bracket for iliopsoas and erector spinae muscles on both sides, and 108 is the adjustment factor. The accuracy of the JOHAS index for identifying sarcopenia, as determined by BIA, was examined using a receiver operating characteristic (ROC) curve analysis on a sample of 639 patients (331 men and 308 women).

The JOHAS index was able to discriminate sarcopenia with an area under the curve (AUC) of around 0.88 in men and 0.75 in women. The JOHAS index outperformed commonly used indices such as the psoas muscle index, erector spinae muscle index, intramuscular adipose tissue content, prognostic nutritional index, and neutrophil/lymphocyte ratio.

The JOHAS index is a promising, pragmatic surrogate for SMI measured by BIA. The recommendable cut-off values are 43 (sensitivity 0.7722, specificity 0.8362) for men and 32 (sensitivity 0.6377, specificity 0.7423) for women.