The Comparability of Functional Assessment of Chronic Illness Therapy - Fatigue Scores between Cancer and Systemic Sclerosis. Issue 1 (January 2017)

• Record Type: Journal Article
• Authors: Coroiu, Adina; Kwakkenbos, Linda; Levis, Brooke; Hudson, Marie; Baron, Murray; Cella, David; Thombs, Brett D.
• Is Part Of: Journal of scleroderma and related disorders. Volume 2:Issue 1(2017)
• Page Start: 57
• Page End: 63
• Publication Date: 2017-01
• Subjects: Cancer -- Differential item functioning -- FACIT-F -- Measurement equivalence -- Systemic sclerosis; Scleroderma (Disease) -- Periodicals; Systemic scleroderma -- Periodicals; Fibrosis -- Periodicals; 616.544
• DOI: 10.5301/jsrd.5000227
• Languages: English
• ISSNs: 2397-1983

Abstract

Purpose: The functional assessment of chronic illness therapy-fatigue (FACIT-F) is commonly used to assess fatigue across diseases. The degree to which the FACIT-F demonstrates measurement equivalence across disease groups, however, is not known. The purpose of this study was to assess differential item functioning (DIF) of FACIT-F items between patients with cancer and systemic sclerosis (SSc or scleroderma). Methods: Secondary analysis of FACIT-F data from cancer and SSc patients. Confirmatory factor analysis was used to assess the factor structure of the FACIT-F in cancer and SSc patients. The multiple-indicator, multiple-cause model was utilized to assess DIF, comparing responses from cancer and SSc patients. Results: A unidimensional factor structure for the FACIT-F was demonstrated with the cancer (n = 1141), SSc (n = 1186), and combined samples. Statistically significant, but small-magnitude, DIF was found for four items. Compared to cancer patients with the same level of fatigue, SSc patients had lower scores (more fatigue) for item 2 ( bodily weakness ), 7 ( energy ), and 8 ( ability to perform daily activities ); and higher scores (less fatigue) for item 9 ( need to sleep throughout the day ). For the entire scale, SSc patients had 0.47 SD lower FACIT-F latent factor scores (more fatigue) than cancer patients. After correcting for DIF, there was a change of only 0.03 SD in this difference (0.44 SD lower). Conclusions: Although statistically significant DIF was detected for four FACIT-F items, the magnitude was small and the effect on fatigue latent scores was minimal. Thus, FACIT-F scores can be used equivalently in cancer and SSc.