Assessing fatigue in persons with cancer: an instrument development and testing study

BACKGROUND: Cancer-related fatigue (CRF) is a highly prevalent, subjective experience of patients with and survivors of cancer. Effective assessment of the attributes of CRF from the patient's perspective is essential. The current study developed a measure of CRF from the patient's perspective and determined its psychometric properties for patients with cancer undergoing chemotherapy. METHODS: Chemotherapy outpatients in a free-standing metropolitan area cancer clinic participated in the current multiphase study. In the instrument development phase, 42 items were generated from a qualitative study with 10 semistructured individual interviews and 6 daily fatigue diaries. These items were revised based on content evaluation by 20 cancer patient content experts. In the instrument analysis phase, the 30 content-validated items were pilot tested by 30 patients with breast carcinoma using cognitive interview techniques. The psychometric properties of the resulting 16-item, 5-point CRF rating scale were tested with 82 patients with breast carcinoma. RESULTS: Principal axis factoring gave a one-factor solution accounting for 59% variance. Coefficient alpha reliability was 0.95 for the final 15-item scale. Convergent validity with the Schwartz Cancer Fatigue Scale was 0.84, concurrent validity with the Geriatric Depression Scale was 0.61, and predictive validity with the Cancer-Related Fatigue Distress Scale was 0.83. CONCLUSIONS: This newly developed instrument to assess the subjective fatigue symptoms of patients with cancer demonstrated effective use of diary and interview methods in instrument development and both cognitive interviewing and traditional psychometric techniques in instrument analysis. The instrument has promising psychometric properties, but confirmatory testing is needed.