Cancer-related Fatigue

Prevalence, Assessment and Treatment Strategies

Joachim Weis

Disclosures

Expert Rev Pharmacoeconomics Outcomes Res. 2011;11(4):441-446. 

In This Article

Measurement of CRF

Assessment and clinical diagnosis of CRF is an important task of healthcare professionals in cancer care. There is a broad expert consensus that CRF, as a complex and subjective phenomenon, can only be measured by self-report assessment tools. Therefore, it has been commonly accepted that self-reports of patients are the most reliable and valid measurements of fatigue.[37,38] In addition, medical history, physical examination, laboratory data and behavior descriptions by relatives are important sources for diagnosing CRF. For clinical assessment, a review of additional medications (e.g., cardiac medications, thyroid medication, sedating medications, such as opioids, benzodiazepines or SSRIs, or TCAs) is also required, especially in multimorbid patients as the medication itself or interactions between different drugs may contribute to increased fatigue.[101]

During the last decade, interest in fatigue among cancer patients has increased considerably and numerous instruments have been developed using different methodologies.[37,38] A review of the research literature shows that CRF may be assessed by either unidimensional or multidimensional instruments. Unidimensional instruments (e.g., Functional Assessment of Chronic Illness Therapy Fatigue module developed by Cella et al.[39] or Brief Fatigue Inventory developed by Mendoza et al.[40]) focus only on physical symptoms of fatigue, whereas multidimensional instruments (e.g., Multidimensional Fatigue Inventory by Smets et al.[41]) address physical, affective and cognitive aspects of CRF. Most of the existing cancer specific questionnaires use a multidimensional approach to measuring CRF,[37] which is in line with an understanding of CRF as a multifaceted syndrome. Most of the scales pertain to intensity, and in addition some ask for interferences with activities of daily living or quality of life. Sensitivity to change over time has been proven only for a few of these instruments. In general, there are a number of key psychometric criteria to be met in the assessment of fatigue to ensure meaningful results. However, not all existing fatigue measures fulfil these requirements. The methodology used for developing the questionnaires does not include any cross-cultural validation, while the concept of fatigue may be different from one country to another. Most of the instruments were developed in the USA with mainly Caucasian patients. For some instruments, no clear explanation is given regarding the procedure followed for development. It is not readily apparent if all developers of the instruments have conducted a pretest of the instrument before giving it to a large number of patients. In addition, some of the questionnaires may be too long to be filled in by CRF patients. The existing questionnaires vary largely with respect to the criteria of validity, reliability, sensitivity to change or cross-cultural applicability. Methods used for supporting claims of construct validity include known groups comparisons, analyses for convergent and discriminant validity. Moreover, cultural background also influences the way the issue of fatigue is considered, for example, in a particular culture, the physical aspects of fatigue may be seen as more important than the social or psychological aspects of fatigue.[42] In conclusion, while many of the fatigue measures reported have both strengths and limitations, no blanket recommendation can be made as to which measure is more appropriate; which instrument the clinician or researcher should use depends primarily on the setting. It is clear that in certain circumstances one measure may be more appropriate than another. While many new tools have been developed over the past decade, future instruments have to be developed by choosing a predefined strict methodology in order to fulfil the need of a high standard measurement tool for CRF. To summarize, there is no gold standard for measuring CRF, but the self-report approach is the commonly chosen strategy for developing such assessment tools. Owing to economic aspects, the questionnaire approach is favored by most of the authors, although there is some evidence that the interview strategy might additionally clarify the complexity of the syndrome.

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