Diagnostic criteria of cachexia and their assessment: decreased muscle strength and fatigue

Purpose of review The classification of cachexia or wasting disease is currently being revised to improve clinical trial design and clinical care. Decreased muscle strength and fatigue are proposed as diagnostic criteria for cachexia or wasting disease including, but not limited to, cancer. This review discusses their expected value in cancer cachexia. Recent findings Fatigue is frequent and multifactorial in cancer patients with limited value to predict cachexia, however, most cachectic patients have fatigue. Its assessment requires multimodal subjective instruments, for outcome monitoring many other fatigue cofactors need to be controlled. Cachexia seems a dominant cause for decreased muscle strength. Most cachectic patients lose muscle strength, usually together with reduced muscle mass. High-individual variability of muscle strength limits its use to longitudinal monitoring. Physical activity monitoring, applying also body-worn sensors, offers additional monitoring tools. Summary To diagnose and monitor cachexia, muscle strength should be measured directly, whereas fatigue is seen as a global outcome.