Problem statement: Several investigators have indicated that case definitions for Chronic Fatigue Syndrome (CFS) are characterized by vaguely worded criteria that lack operational definitions and guidelines. The most widely used CFS case definition is the Fukuda et al. criteria, which uses polythetic criteria (i.e., patients are only required to have four out of a possible eight symptoms). Yet two of these eight symptoms (post-exertional malaise and memory/concentration problems) are an essential feature of this illness and the Fukuda et al. criteria do not require that these symptoms be present among all patients. Significant methodological problems could occur if investigators in different settings recruit samples with different percentages of these core symptoms. In contrast, the Canadian clinical case definition does require specific ME/CFS symptoms such as post-exertional malaise and memory/concentration problems. The provision of operationally explicit, objective criteria on specific key symptoms might reduce criterion variance as a source of unreliability. In addition, the use of structured interview schedules will ensure that symptoms are assessed in a consistent way across settings. Conclusion/Recommendations: In this article, we specified explicit rules for determining whether critical symptoms meet ME/CFS criteria using a revised Canadian case definition and a questionnaire has been developed to assess core symptoms. It is hoped that these developments will lead to increased reliability of this revised Canadian case definition as well as more frequent use of these criteria by investigators.
Purpose All of the major current case definitions for chronic fatigue syndrome (CFS) specify substantial reductions in previous levels of occupational, educational, social, or personal activities to meet criteria. Difficulties have been encountered in operationalizing “substantial reductions.” For example, the Medical Outcomes Study Short Form-36 Health Survey (SF-36) has been used to determine whether individuals met the CFS disability criterion. However, previous methods of using the SF-36 have been prone to including people without substantial reductions in key areas of physical functioning when diagnosing CFS. This study sought to empirically identify the most appropriate SF-36 subscales for measuring substantial reductions in patients with CFS. Method The SF-36 was administered to two samples of patients with CFS: one recruited from tertiary care and the other a community-based sample; as well as a non-fatigued control group. Receiver operating characteristics were used to determine optimal cutoff scores for identifying patients with CFS. Results The SF-36 Role-Emotional subscale had the worst sensitivity and specificity, whereas the Vitality, Role-Physical, and Social Functioning subscales had the best sensitivity and specificity. Conclusion Based on evidence from this study, potential criteria for defining substantial reductions in functioning and diagnosing CFS is provided.
Few studies have explored issues of sensitivity and specificity for using the fatigue construct to identify patients meeting chronic fatigue syndrome (CFS) criteria. In this article, we examine the sensitivity and specificity of several fatigue scales that have attempted to define severe fatigue within CFS. Using Receiver Operating Characteristic (ROC) curve analysis, we found most scales and sub-scales had either significant specificity and/or sensitivity problems. However, the postexertional subscale of the ME/CFS Fatigue Types Questionnaire (Jason, Jessen, et al., 2009) was the most promising in terms of specificity and sensitivity. Among the more traditional fatigue scales, Krupp, LaRocca, Muir-Nash, and Steinberg's (1989) Fatigue Severity Scale had the best ability to differentiate CFS from healthy controls. Selecting questions, scales and cut off points to measure fatigue must be done with extreme care in order to successfully identify CFS cases. Keywordschronic fatigue syndrome; fatigue; fatigue scales; sensitivity and specificity There have been relatively few studies assessing the sensitivity and specificity of fatigue scales which are frequently used to identify individuals with chronic fatigue syndrome (CFS) and differentiate them from healthy controls. The present investigation consists of two distinct studies, both of which employ samples of individuals with CFS and controls, and to assess the effectiveness of several well known fatigue instruments in discriminating between these two groups by utilizing Receiver Operating Characteristic (ROC) curve analyses. The Fukuda et al. (1994) CFS case definition is the currently accepted case definition internationally, although there is no available "gold standard" to assess fatigue severity. This case definition requires an individual to experience six or more months of persisting or recurring chronic fatigue and the co-occurrence of four of eight additional core symptoms. However, these Fukuda et al. requirements have been criticized as lacking operational definitions and guidelines for accurate identification of CFS cases (Jason, King, et al., 1999;Reeves et al., 2003). For example, these criteria do not specify how to assess fatigue severity or the presence of persisting or recurring fatigue for a period of 6 or more months. Partially in response to these problems with operationalizing the Fukuda et al. definition, the Centers for Disease Control and Prevention (CDC) developed an empiric case definition for CFS that involves assessment of symptoms, disability, and fatigue with standardized instruments and specific cutoff points .Correspondence concerning this article should be addressed to Leonard A. Jason, Ph.D., Director, Center for Community Research, 990 W. Fullerton Ave., Suite 3100, Chicago, Il. 60614. telephone: 773-325-2018; fax: 773-325-4923 et al., 2007), rates that are about ten times higher than prior CDC prevalence estimates (Reyes et al., 2003) and estimates of other investigators . It is plausible that this inflated CFS prevalence...
The present natural history study examined the course of CFS from 1995–1997 (Wave 1) to approximately ten years later (Wave 2) from a random, community-based, multi-ethnic population.. The rate of CFS remained approximately the same over the period of time from Wave 1 to Wave 2, although a high level of mortality was found (18% of those with medical or psychiatric exclusions group, 12.5% for the CFS group). Physical measures of disability and fatigue, along with measures of specific somatic symptoms, better differentiate individuals who later are diagnosed with CFS than more psychosocial measures such as stress and coping.
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