Purpose: To derive from the Patient Reported Outcomes Measurement Information System (PROMIS) fatigue item bank, a short form for individuals with multiple sclerosis (MS), the PROMIS-Fatigue(MS).
Methods: A panel of 37 clinicians and 46 individuals with MS ranked the relevance of PROMIS fatigue items to persons with MS. Eight items were selected for the PROMIS-Fatigue(MS) that maximized relevance rankings, content coverage, and item discrimination. The PROMIS-Fatigue(MS) and an existing, 7-item PROMIS fatigue short form (PROMIS-Fatigue(SFv1.0)) were administered to a new sample of 231 individuals with MS. Known groups and content validity were assessed.
Results: Scores from the short forms were highly correlated (r = 0.92). Discriminant validity of the PROMIS-Fatigue(MS) scores was supported in known groups comparisons. Scores of neither short form exhibited an advantage in quantitative analyses. The PROMIS-Fatigue(MS) targeted more of the content included in participants' responses to open-ended questions than did the PROMIS-Fatigue(SFv1.0).
Conclusions: The PROMIS-Fatigue(MS) was derived to have content validity in MS samples. The validity of the measure was further supported by the ability of PROMIS-Fatigue(MS) items to discriminate among groups expected to differ in levels of fatigue. We recommend its use in measuring the fatigue of individuals with MS.