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1. Introduction Symptom-evaluating studies investigate the prevalence, aetiologies and the prognosis of certain symptoms in well-defined medical care settings. In this dissertation a survey of those studies on tiredness as a symptom in primary care is presented. Tiredness is a multi-layered, subjective state, which may be physiological and harmless, but sometimes occurs in the context of psychological or somatic illnesses. Since tiredness is a broad term with a variety of meanings, a symptom-oriented approach is recommended for the general practitioner. For him it is important to be able to assess the likelihood of a patient suffering from tiredness to have an illness that requires treatment in order to prevent avertable dangerous consequences. Preliminary results of this meta-study have already been included in the updated DEGAM-Leitlinie. 2. Methods After specifying a detailed search syntax the pertinent publications were identified from Medline and Embase, using predefined inclusion criteria. Additionally a manual search was conducted in the congress indices of the European General Practice Research Network and the North American Primary Care Research Group, and the references of the already included papers were inspected to find further potentially relevant studies. Two independent reviewers examined whether the studies met our previously defined inclusion and exclusion criteria. The results of all relevant papers were extracted and discussed in detail. The quality of the studies was evaluated in terms of fourteen defined criteria. 3. Main Results 81 studies from the literature search were included in the survey. They show that tiredness is a widespread health grievance. However the studies were quite heterogeneous so that subgroups that were suitable for a quantitative synthesis were frequently selected. Particularly high prevalences of up to about 70% were found if the patients were systematically interviewed about the symptom. Without being explicitly asked, 13–26% of the patients complained about tiredness as a primary or secondary reason of consultation. Studies taking into account only patients complaining about tiredness as their main symptom indicated lower frequencies; Studies that were comparable in their key features yielded a point estimate of 4.1%. For the majority of patients tiredness was associated with psychological disorders, in particular depression and anxiety. Severe somatic causes occured rarely, provided that the definitions of the illnesses were not too broad and criteria pointing at a causal relation (such as a temporal relation) were taken into account. About 2.1% of the patients who have spontaneously complained about tiredness had anemia. Malignancies were diagnosed for less than 1% of the patients in all studies in which tiredness was not systematically interrogated. Some papers investigated the prevalence of the chronic fatigue syndrome. In studies in which not only those patients were defined as “tired” who already satisfied the main criteria of CFS, it was detected that in primary care only a small portion of patients (less than 5%) with the symptom tiredness suffered from CFS. For the majority of patients tiredness was still present after several months but only approximately 5% of them returned to the general practitioner because of this symptom. 4. Discussion and Conclusions This survey provides quantitative evidence that tiredness is a very frequent health problem in primary care. For the general practitioner knowledge about the different degrees of severity of tiredness is of great importance. Tiredness can be a harmless symptom that patients only mention when they are systematically interviewed, but also a chronic condition, seriously lowering the quality of life. The evaluation was difficult because the quality of some studies showed serious deficiencies. These studies could not be included in the statistical analysis. The quantitative synthesis was occasionally problematic and only possible for subgroups since the studies differed strongly in their clinical and methodological characteristics. The survey shows that tiredness can occur as an isolated, transitory condition but also in the context of various psychological and somatic diseases. For the physician in charge it is important to keep in mind that tiredness can have various causes and that in many cases a multi-factorial background has to be assumed. Since severe somatic causes for tiredness in primary care patients are rarely found, a comprehensive and expensive diagnostic investigation is not appropriate if no specific indications are present. Tiredness is often associated with psychological disorders so that a thorough anamnesis including psychological symptoms especially concerning depressive disorders is recommended.