Development and psychometric evaluation of the Severity of Myalgic Encephalomyelitis Scale (SoMES) and the Myalgic Encephalomyelitis Occupational Status Scale (MEOSS)

In adults with myalgic encephalomyelitis/chronic fatigue syndrome, the Severity of ME Scale (SoMES) and ME Occupational Status Scale (MEOSS) show moderate-to-excellent psychometric performance, including SoMES test-retest k=0.53 and MEOSS k=0.76.

• Why it matters: Existing tools for measuring ME/CFS severity and occupational impact are limited, so brief, psychometrically supported assessments are needed for consistent evaluation and sensitivity to differences in functioning.
• What they did: The SoMES and MEOSS were co-produced from literature and lived experience, then tested in an online survey of 995 adults with ME/CFS with retesting after two weeks in 579 participants. Validity used SF-36 physical function correlations and Kruskal-Wallis discriminant tests; reliability used weighted kappa and minimal detectable difference (MDD).
• The result: SoMES criterion validity was moderate-good (r=0.663, p<0.001) and MEOSS was moderate (r=0.472, p<0.001), with discriminant validity across SF-36 physical function levels (p=0.003–0.0001). Test-retest reliability was moderate for SoMES (k=0.53, P<0.001; MDD=1.6) and excellent for MEOSS (k=0.76, p<.001; MDD=1.4).

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