Original ArticleLinking Fatigue Measures on a Common Reporting Metric

ContextFatigue is one of the most common and debilitating symptoms experienced by patients living with chronic conditions and is also commonly experienced in the general U.S. population. Linking fatigue scores from some of the most widely used measure of fatigue to the same metric will facilitate interpretation of fatigue outcomes.ObjectivesThe goal of this study is to report the methods used to develop linking (crosswalk) tables to enable the direct comparison of Patient-Reported Outcomes Measurement Information System-Fatigue with fatigue scores on the Functional Assessment of Chronic Illness Therapy-Fatigue Scale, the Medical Outcomes Study Short Form-36 four-item Vitality Scale, and the Quality of Life in Neurological Disorders Fatigue Scale.MethodsParticipants were recruited from two data sets (n = 1120 and n = 803). Two item response theory-based linking methods, the Stocking-Lord calibration and fixed-parameter calibration, were used to establish linking between measures. The item response theory calibrations were derived using the graded response model.ResultsBoth the Stocking-Lord calibration and fixed-parameter calibration linking methods produced comparable results. Final crosswalk tables are reported for the fixed-parameter calibration.ConclusionFindings can facilitate comparison of scores across some of the most widely used fatigue measures and assist in comparing patient-reported fatigue outcomes in clinical trials, comparative effectiveness research, and clinical practice.