Wilburn J, McKenna S, Twiss J, Kemp K, Campbell S. Validating the Unidimensional Fatigue Impact Scale (U-FIS) for use in Crohn's disease. Poster presented at the 2013 ISPOR 16th Annual European Congress; November 2013. Dublin, Ireland. [abstract] Value Health. 2013 Nov; 16(7):A499. doi: 10.1016/j.jval.2013.08.1128.

OBJECTIVES: Fatigue is usually defined as a feeling of exhaustion, lack of energy or tiredness and affects many aspects of daily living. Crohn's Disease (CD) is often associated with severe fatigue. The Fatigue Impact Scale (FIS) was developed to determine the mental and physical impacts of fatigue. It has been simplified and shortened to 22 items and shown by Rasch analysis to be unidimensional. This version is called the U-FIS. The study was designed to determine the validity of the U-FIS when used with CD patients.

METHODS: CD patients were asked to complete the U-FIS and a subset of respondents completed it again two weeks later to assess test-retest reliability. Rasch analysis was applied to U-FIS data to determine unidimensionality. Construct validity was further assessed by relating scores on the U-FIS to those on the Crohn’s Life Impact Scale (CLIQ) and the Nottingham Health Profile (NHP).

RESULTS: A total of 158 CD patients (36.1% female; aged 16-79 years (mean: 42.4; SD 15.0)) completed the U-FIS, with 103 completing it a second time. Overall fit to the Rasch model was confirmed (p = 0.61) and no items misfit. Internal consistency (0.98) and reproducibility (test-retest reliability = 0.88) for the U-FIS were good. U-FIS scores correlated 0.79 with those on the CLIQ indicating the importance of fatigue to quality of life. U-FIS scores were also related as expected with NHP section scores.

CONCLUSIONS: The U-FIS is a reliable and valid instrument for measuring fatigue in Crohn’s Disease. These findings replicate those found with the use of the measure with patients who have Multiple Sclerosis. The U-FIS is valuable as it provides a holistic index of the impact of fatigue from the patient’s perspective. The measure may prove valuable for use with patients who have a wide variety of chronic conditions.

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