Content Validity and Psychometric Evaluation of the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) in Patients with Crohn's Disease and Ulcerative Colitis.

These results highlight the importance of fatigue among adolescents and adults with CD or UC and provide evidence that the FACIT-Fatigue is content valid and produces reliable, valid, and interpretable scores in these populations. Care should be taken if using the questionnaire with adolescents who may be less familiar with the word "fatigue." Clinical trial registration numbers NCT03105128 (date of registration: 4 April 2017) and NCT02819635 (date of registration: 28 June 2016).