Development of a Fatigue and Functional Impact Scale in anemic cancer patients receiving chemotherapy

BACKGROUND. This study was conducted to develop a brief measure of fatigue and functional impact in cancer patients with anemia. METHODS. Data were obtained from a multisite, phase 2 study of darbepoetin-α (n = 1558). Eligible patients were ≥18 years with nonmyeloid malignancies and anemia (hemoglobin ≤11 g/dL who were receiving chemotherapy. Items from the Functional Assessment of Cancer Therapy-Fatigue (FACT-F), Brief Fatigue Inventory (BFI), Fatigue Symptom Inventory (FSI), and items adapted from the Medical Outcomes Study SF-36 physical functioning scale were evaluated for inclusion in the measure. Items were selected by identifying the best predictors of total FACT-F scores, hemoglobin, and adjusted maximum oxygen uptake (VO ₂Max) in regression models. Correlations were examined between scale scores and adjusted VO₂Max, hemoglobin, performance status, self-reported energy, and productivity. RESULTS. Data from 401 patients with complete data were used to identify 8 items for the Fatigue and Functional Impact Scale (FFIS), which was then evaluated using 1355 of the 1558 patients. The FFIS had an estimated internal consistency reliability of 0.90. The FFIS had significant correlations with the FACT-F (r = 0.94), FSI (r = 0.80), and BFI (r = 0.86), from which it was derived. The FFIS also correlated substantially with single-item measures of energy (r = 0.75) and productivity (r = 0.72). CONCLUSIONS. The FFIS is a reliable, brief, and practical tool that is potentially suitable for identifying fatigue ana functional impact in cancer patients.