Some have argued that these changes should not be seen as merely different scoring schemes, but as different versions of the same scale. The data showed that 22 participants showed improvement at the primary trial endpoint based on one scoring method, while the other scoring method showed a decline. Internal consistency and convergent validity[ edit edit source ] The Chalder fatigue scale has been shown to have good internal consistency, as indicated by a split half reliabilities of 0. Cronbach alpha for the item fatigue scale Chalder et al.
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Abstract 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.
Selecting questions, scales and cut off points to measure fatigue must be done with extreme care in order to successfully identify CFS cases. Keywords: chronic 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. 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. 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.
Reeves et al. In addition, reduced activity scale items refer to issues that a person with depression might easily endorse. With the Reeves et al. It is plausible that this inflated CFS prevalence estimate in the U. As an example of a measure of fatigue intensity alone, Chalder et al. Using an ROC curve analysis, Jason et al. In addition, Goudsmit, Stouten, and Howes found there was a marked overlap in fatigue scores within a CFS sample between those patients who rated themselves as moderately ill and those who rated themselves as severely ill.
The FSS is composed of nine items, and in the initial validation study, internal consistency was high for specific illness groups MS and lupus and healthy controls. A ceiling effect in the FSS may limit its utility to assess severe fatigue-related disability, and Stouten has warned that many fatigue scales do not accurately represent the severe fatigue that is uniquely characteristic of CFS.
Other fatigue scales have also been developed for assessing fatigue severity and related functioning Fukuda et al. Each item on the PFRS lists a symptom typical of CFS and respondents are asked to indicate how intensely they have experienced that symptom over the past week. Ray et al. However, fatigue is a multifaceted construct, and a closer examination of the PFRS Fatigue factor items suggests that many different fatigue states are subsumed in this subscale.
Consequently, this suggests that fatigue instruments might need to be developed that delineate finer shades of meaning in the context of the physical fatigue experienced by individuals with CFS. Recently, Jason, Jessen, et al. Fatigue items encompassed the following dimensions: lack of energy resources needed for daily functioning, over-stimulation of the mind or body without the available energy to act out the mental or physiological excited state, exhaustion or interruption related to everyday cognitive processes, tiredness that is associated with physical symptoms commonly seen in cases of influenza, and abnormal exhaustion following physical activity.
The five-factor structure confirmed in the CFS sample suggests that the symptom of fatigue in this illness is a multi-dimensional entity that is distinct from the generalized form of fatigue experienced by healthy individuals. The MFTQ has been compared to other fatigue scales, and some intriguing findings have emerged. For example, Jason, Jessen, et al. These correlations suggest that for the general population, symptoms of post-exertional malaise are significantly related to emotional distress, whereas when people with CFS report symptoms of post-exertional malaise, the symptoms are independent of emotional distress.
It is possible that because healthy individuals experience this relationship between emotional distress and post-exertional malaise, they might also believe these two domains are connected for themselves and, by inference, for patients with CFS, when in fact Jason, Jessen, et al.
If fatigue scales are to be recommended for use in the diagnosis of CFS, as has been proposed by Reeves et al. The current investigation sought to assess this critical issue by examining two distinct samples. The implications of appropriate and inappropriate levels of sensitivity and specificity of these scales are far reaching with regards to obtaining well-characterized research samples. Ultimately, this leads to more ambiguity about the nature of CFS and further stigmatization of individuals disabled by this chronic illness.
These participants were initially contacted and recruited through several chronic fatigue syndrome support groups, conferences, and newsletters. Post-Exertional fatigue was defined as abnormal exhaustion following a bout of physical activity e. Wired fatigue was considered an over stimulation of the mind or body without the available energy to act out the mental or physiological excited state e. Brain Fog fatigue constituted the exhaustion or interruption related to everyday cognitive processes, such as memory recall, speech, or information processing e.
Energy fatigue was defined as a lack of energy resources needed for daily functioning e. Finally, Flu-Like fatigue was the tiredness that is associated with physical symptoms commonly seen in cases of influenza e. A composite score for each item was then calculated by multiplying the symptom rating score by the frequency score, with a possible range 0 to Each scale score is an average of item composite scores for that scale.
For the CFS sample, five factors emerged, but for the control sample, only one general factor emerged Jason, Jessen, et al. These values demonstrate high internal consistency for the MFTQ on both samples. In the original scale development study, Krupp et al. Krupp, Jandorf, Coyle, and Mendelson used this scale with 72 patients with CFS, and the mean fatigue score was 6.
The scores are then summed and a higher score indicates more severe fatigue-related symptomatology. Profile of Fatigue-Related Symptoms Ray et al. Each item lists a symptom typical of CFS and respondents are asked to indicate how intensely they have experienced that symptom over the past week. Responses are given in a seven point Likert-scale format ranging from 0 not at all through 3 moderately to 6 extremely. Average item scores are then computed for four separate factors: Emotional Distress, Fatigue, Cognitive Difficulty, and Somatic Symptoms.
Scale reliability was assessed for each factor, with alpha coefficients ranging from. The ROC curve graphically represents the probability of true positive results in diagnosis as a function of the probability of false positive results of this test.
Sensitivity is defined as the probability that the test correctly classifies a CFS subject as positive. A true positive is defined as a participant who scores positive on the fatigue test for CFS and actually has the illness, whereas a false positive occurs when a participant whose fatigue tests positive for CFS does not have the illness.
Specificity involves a test correctly classifying a non-ill participant as negative. A true negative is defined as a participant who tests negative on the fatigue test for CFS and does not have the illness, whereas a false negative is defined as a participant who tests negative on the fatigue test for CFS and actually has the illness. Results Sample Characteristics Of the participants that were enrolled in the study with possible CFS, eight were excluded from the analysis because they indicated they were never officially diagnosed with CFS.
The final sample thus consisted of individuals who reported being diagnosed by a physician with CFS and had full information for each of the fatigue scales. The control group consisted of individuals. There were significant differences between the CFS and control samples for all variables, including: age, gender, race, Hispanic origin, marital status, educational attainment, and work status. Socio-demographic information can be found in Jason, Jessen, et al.
ROC analyses An ROC analysis is produced by plotting the sensitivity versus 1 - specificity for all cutoff points of the fatigue scales. The AUC is a summary measure that essentially averages diagnostic accuracy across the spectrum of test values.
The informative AUC ranges from 0. An AUC of. Control Scale.
Fatigue Assessment Scale (FAS)
Search Menu The Fatigue Scale, sometimes referred to as the Chalder Fatigue Scale the CFQ—to differentiate it from chronic fatigue syndrome or CFS , is a self-administered questionnaire for measuring the extent and severity of fatigue within both clinical and non-clinical, epidemiological populations. Tiredness and fatigue are important in both academic and applied occupational medicine—and the understanding of the link between them and employee health, performance, safety and general workability continues to grow. The need for a reliable self-completion tool that can measure this subjective condition, either in extreme clinical cases or in routine day-to-day functioning, has never been greater [ 3 ]. As a short questionnaire, phrased in simple English with a straightforward answering system, it provides a brief tool to measure both physical and psychological fatigue.
Fatigue Scales and Chronic Fatigue Syndrome: Issues of Sensitivity and Specificity