Psychometric Evaluation of the Korean Version of the Functional Assessment of Chronic Illness Therapy-Fatigue.

Background: The Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) instrument is a fatigue measure widely used on patients with cancer worldwide. The psychometric quality of the Korean version of the FACIT-Fatigue instrument has never been systematically evaluated.

Purpose: The purpose of this study was to assess the reliability and validity of the Korean version of the FACIT-Fatigue instrument.

Methods: This study used data collected from 170 patients with cancer and 120 healthy individuals. Internal consistency reliability was analyzed using Cronbach's α and item-total correlation. Construct validity was analyzed using confirmatory factor analysis, and known-group validity was tested using t tests. Convergent validity was analyzed using Pearson's correlation with pain and functional limitations. Predictive validity was analyzed using receiver operating characteristic curves.

Results: The Cronbach's α was .93 for the reliability evaluation, and the item-total correlation ranged from .27 to .84. In the construct validity evaluation, the bifactor model showed good fit (Q = 1.93, comparative fit index = .97, Tucker-Lewis index = .96, root mean square error of approximation = .05), indicating using the instrument's total score to be more appropriate than using the subscale scores (explained common variance = .76, ω = .95, ωH = .85, ωH/ω = .89). The group of patients with cancer showed significantly higher fatigue than the healthy subject group, showing known-group validity (t = -10.40, p < .05). Fatigue showed significant and strong correlations with functional limitations and pain (all ps < .001). The area under the curve was .81 (cutoff point = 40, Youden's index: 0.47, sensitivity: 77.60%, specificity: 73.04%), verifying that the instrument is predictive of higher fatigue severity in patients with cancer.

Conclusions/implications for practice: The Korean version of the FACIT-Fatigue instrument was shown to be reliable and valid. Its construct validity supports the use of the total scale score rather than the subscale scores.