Comparison of proposed diagnostic criteria with FACT-F and VAS for cancer-related fatigue: proposal for use as a screening tool.

The objective was to validate the use of the proposed International Statistical Classification of Diseases and Related Health Problems (10th revision) (ICD-10) criteria for fatigue (P-ICD10) through comparison with the Functional Assessment of Cancer Therapy Fatigue (FACT-F) subscale and three visual analogue scale (VAS) qualities in cancer patients thought to be fatigued. Fatigue was assessed in 834 cancer patients at three clinical centres in Belgium, using P-ICD10, FACT-F, and VAS to assess: level of energy (VAS1), quality of life (VAS2), and ability to perform daily activities (VAS3). Of the 834 interviewed cancer patients, 54% were classified as fatigued by the P-ICD10 criteria. Internal consistency of P-ICD10 was very good (alpha coefficient 0.82). The principal component analysis corroborated good internal consistency with all variables included in the first component; a second component was used to identify psychological fatigue (concentration and short-term memory disabilities). An abridged set of screening tools based on the first three general symptoms of the P-ICD10 is proposed with 100% specificity and 86% specificity, respectively. There was a marked decrease in FACT-F and VAS1 scores in patients diagnosed as fatigued by the P-ICD10 (mean+/-SD, FACT-F 20+/-9 vs 39+/-8, VAS1 34+/-21 vs 61+/-21). A logistic regression model between P-ICD10 criteria diagnosis and FACT-F (VAS1) identified a score of 34 (61) on the FACT-F scale as a proposed cut-off point for the diagnosis of fatigue. The ICD-10 criteria can be recommended as a diagnostic tool, whereas the FACT-F scale and the level of energy 100-mm VAS assess the intensity of fatigue, and are more suitable for follow-up of cancer-related fatigue.