Measuring fatigue in patients with cancer.

Our current state of knowledge of the fatigue experienced by patients with cancer is limited, and further development is hampered by the definitions of fatigue, which remain numerous, inconsistent, and varied according to the discipline of the author and the nature of the research. It is fairly well established within the healthcare literature that it is multidimensional in nature. This has implications for the reliable and valid assessment of this phenomenon. There are a number of instruments currently available with which to measure cancer-related fatigue. These include instruments developed for use initially with healthy populations, such as airmen and workers engaged in manual and clerical work. However, cancer-specific fatigue assessment instruments are now available, and are preferable to those instruments developed without reference to this patient group. Fatigue is often found as a single item or scale in self-report measures of symptoms, mood and functional status reflecting the effect of fatigue and the interaction of fatigue with other symptoms or concepts related to quality of life. Factors to be considered in selecting a measure of fatigue for research will be outlined, and recommendations for the future development and validation of useful and scientifically credible measures of fatigue made.