ObjectiveTo identify case definitions for chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME), and explore how the validity of case definitions can be evaluated in the absence of a reference standard.DesignSystematic review.SettingInternational.ParticipantsA literature search, updated as of November 2013, led to the identification of 20 case definitions and inclusion of 38 validation studies.Primary and secondary outcome measureValidation studies were assessed for risk of bias and categorised according to three validation models: (1) independent application of several case definitions on the same population, (2) sequential application of different case definitions on patients diagnosed with CFS/ME with one set of diagnostic criteria or (3) comparison of prevalence estimates from different case definitions applied on different populations.ResultsA total of 38 studies contributed data of sufficient quality and consistency for evaluation of validity, with CDC-1994/Fukuda as the most frequently applied case definition. No study rigorously assessed the reproducibility or feasibility of case definitions. Validation studies were small with methodological weaknesses and inconsistent results. No empirical data indicated that any case definition specifically identified patients with a neuroimmunological condition.ConclusionsClassification of patients according to severity and symptom patterns, aiming to predict prognosis or effectiveness of therapy, seems useful. Development of further case definitions of CFS/ME should be given a low priority. Consistency in research can be achieved by applying diagnostic criteria that have been subjected to systematic evaluation.
We found that two types of patient-mediated interventions, patient-reported health information and patient education, probably improve professional practice by increasing healthcare professionals' adherence to recommended clinical practice (moderate-certainty evidence). We consider the effect to be small to moderate. Other patient-mediated interventions, such as patient information may also improve professional practice (low-certainty evidence). Patient decision aids may make little or no difference to the number of healthcare professionals' adhering to recommended clinical practice (low-certainty evidence).The impact of these interventions on patient health and satisfaction, adverse events and resource use, is more uncertain mostly due to very low certainty evidence or lack of evidence.
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