Operationalizing Substantial Reduction in Functioning Among Young Adults with Chronic Fatigue Syndrome, by Kristen D. Gleason, Jamie Stoothoff, Damani McClellan, Sttephanie McManimen, Taylor Thorpe, Ben Z. Katz, Leonard A. Jason in International Journal of Behavioral Medicine 2018 pp1-8 [Published online 5 June 2018]
Chronic fatigue syndrome and myalgic encephalomyelitis are fatiguing illnesses that often result in long-term impairment in daily functioning. In reviewing case definitions, Thrope et al. (Fatigue 4(3):175–188, 2016) noted that the vast majority of case definitions used to describe these illnesses list a “substantial reduction” in activities as a required feature for diagnosis. However, there is no consensus on how to best operationalize the criterion of substantial reduction.
operationalization is a process of defining the measurement of a phenomenon that is not directly measurable, though its existence is indicated by other phenomena. Operationalization is thus the process of defining a fuzzy concept so as to make it clearly distinguishable, measurable, and understandable in terms of empirical observations. [Wikipedia]
The present study used a series of receiver operating curve (ROC) analyses to explore the use of the Medical Outcomes Study Short-Form-36 Health Survey (SF-36), designed by Ware and Shelbourne for operationalizing the substantial reduction criterion in a young adult population (18–29 years old). We compared the sensitivity and specificity of various cutoff scores for the SF-36 subscales and assessed their usefulness in discriminating between a group of young adults with a known diagnosis of chronic fatigue syndrome or myalgic encephalomyelitis (n = 98) versus those without that diagnosis (n = 272).
The four top performing subscales and their associated cutoffs were determined: Physical Functioning ≤ 80, General Health ≤ 47, Role Physical ≤ 25, and Social Functioning ≤ 50. Used in combination, these four cutoff scores were shown to reliably discriminate between the patients and controls in our sample of young adults.
The implications of these findings for employing the substantial reduction criterion in both clinical and research settings are discussed.