Psychometric Performance of Fatigue Scales in Inflammatory Bowel Disease

Background Fatigue is highly prevalent in people with inflammatory bowel disease (IBD). Fatigue scales are important for studies testing fatigue interventions, but information about psychometric properties of many scales is insufficient in IBD. We compared the psychometric properties of multiple generic fatigue scales in participants with IBD. Methods Individuals with IBD (N = 216) completed the Daily Fatigue Impact Scale (DFIS), the vitality subscale of the RAND-36, and the Patient Health Questionnaire-9 (PHQ-9) fatigue item twice. A subgroup (n = 84) also completed the Fatigue Impact Scale (FIS) once, from which we also scored the 21 items from the Modified Fatigue Impact Scale (MFIS-IBD). We assessed floor/ceiling effects, construct validity, and internal consistency reliability. Using relative efficiency (RE), we compared discriminating ability and comparative responsiveness of the measures regarding disease activity and employment status and changes. Results The FIS, MFIS, and RAND-36-vitality scales did not exhibit floor or ceiling effects. The DFIS showed mild floor effects (19.4%), and the PHQ-9 fatigue item showed floor (18.1%) and ceiling (20.8%) effects. Internal consistency reliability exceeded 0.93 for FIS, MFIS-IBD, and DFIS and was 0.81 for the RAND-36-vitality scale. In the subgroup analysis, the FIS, MFIS-IBD, and DFIS were strongly correlated with each other (r >= 0.90). The ability to discriminate between disease activity groups was highest for the FIS and MFIS-IBD, followed by the DFIS. The FIS, MFIS-IBD, and DFIS were responsive to changes in work impairment. Conclusions The FIS, MFIS-IBDs and DFIS had adequate validity and reliability for assessing fatigue in IBD. Lay Summary Fatigue is very common in people with inflammatory bowel disease (IBD). Fatigue scales are important for studies testing treatments for fatigue. However, information about how well these fatigue scales measure fatigue is inadequate in IBD. In this study, we compared the how well multiple fatigue scales worked in people with IBD. We focused on scales that can be used in many different clinical populations including the Fatigue Impact Scale (FIS), the Modified Fatigue Impact Scale-IBD (MFIS), the Daily Fatigue Impact Scale (DFIS), RAND-36-vitality scales and Patient Health Questionnaire fatigue item. Scores on the three FIS, MFIS and DFIS were strongly related to each other, and these three scales generally performed well; the others did not. The FIS and MFIS-IBD were best able to discrminate between people with IBD who did and did not have ongoing disease activity.