Validation of the cancer fatigue scale (CFS) in a UK population.

BACKGROUND

Cancer-related fatigue is one of the most common symptoms in patients with cancer. Fatigue reduces health-related quality of life. The Cancer Fatigue Scale (CFS) is a brief instrument that captures the multidimensional nature of fatigue with robust validity. The original scale was developed/validated with Japanese cancer patients. It was our aim to report the psychometric properties of an English translation of the CFS.

METHODS

This cross-sectional study was conducted between February-October 2008 in London, UK. Three groups were recruited: cancer patients (index group), diabetic patients (chronic disease control group), and a healthy control group. All participants completed a questionnaire on recruitment and a subset were retested at 2-8 weeks. Reliability was assessed with analysis of internal consistency (Cronbach's alpha), homogeneity (item-total correlations) and test-retest reliability. Construct validity was assessed with inter-subscale correlations. To assess convergent validity, the correlations between the CFS and FNS, EORTC - QLQ C30, and HADS were examined with Spearman Rank correlation coefficients. The discriminant validity was determined by the known group method.

RESULTS

160 participants were recruited: 60 cancer and 50 diabetes patients, and 50 healthy patients. Cronbach's alphas for the total scale and all three subscales (range 0.83,0.94) were all above the 0.70 criterion suggested for group comparisons thus the CFS showed excellent internal consistency. Homogeneity measures all fulfilled the 0.20 criterion (range 0.53-0.84). Combining the three groups, all test-retest correlations for the CFS and its subscales were above 0.7. Physical and affective subscales showed 100% scaling success. Both scores and sub-scores for the CFS correlated positively (p < 0.001) with FNS and HADS depression and anxiety subscales. The CFS correlated positively (p < 0.001) with all but one item of the EORTC-QLQ C30.

CONCLUSIONS

This evaluation of the measurement properties of the CFS-English shows that it is a reliable and valid tool for assessing key dimensions of cancer-related fatigue.