Psychometric properties of the PROMIS® Fatigue Short Form 7a among adults with myalgic encephalomyelitis/chronic fatigue syndrome
To evaluate the psychometric properties of the Patient-Reported Outcome Measurement Information System® Fatigue Short Form 7a (PROMIS F-SF) among people with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS).
Analyses were conducted using data from the Multi-Site Clinical Assessment of ME/CFS study, which recruited participants from seven ME/CFS specialty clinics across the US. Baseline and follow-up data from ME/CFS participants and healthy controls were used. Ceiling/Floor effects, internal consistency reliability, differential item functioning (DIF), known-groups validity, and responsiveness were examined.
The final sample comprised 549 ME/CFS participants at baseline, 386 of whom also had follow-up. At baseline, the sample mean of PROMIS F-SF T-score was 68.6 (US general population mean T-score of 50 and standard deviation of 10). The PROMIS F-SF demonstrated good internal consistency reliability (Cronbach’s α = 0.84) and minimal floor/ceiling effects. No DIF was detected by age or sex for any item. This instrument also showed good known-groups validity with medium-to-large effect sizes (η2 = 0.08–0.69), with a monotonic increase of the fatigue T-score across ME/CFS participant groups with low, medium, and high functional impairment as measured by three different variables (p < 0.01), and with significantly higher fatigue T-scores among ME/CFS participants than healthy controls (p < 0.0001). Acceptable responsiveness was found with small-to-medium effect sizes (Guyatt’s Responsiveness Statistic = 0.28–0.54).
Study findings support the reliability and validity of PROMIS F-SF as a measure of fatigue for ME/CFS and lend support to the drug development tool submission for qualifying this measure to evaluate therapeutic effect in ME/CFS clinical trials.
KeywordsFatigue Myalgic encephalomyelitis/chronic fatigue syndrome Ceiling/floor effects Internal consistency reliability Differential item functioning Known-groups validity Responsiveness
We would like to thank the Multi-Site Clinical Assessment of ME/CFS (MCAM) study group who made the data sets available through Research Collaboration Agreement. The group included: Division of High-Consequence, Pathogens and Pathology, Centers for Disease Control and Prevention, Atlanta, Georgia: Elizabeth R. Unger, Britany Helton, Yang Chen, and Monica Cornelius; Open Medicine Institute Consortium, Mountain View, CA: Andreas Kogelnik, Catt Phan, Joan Danver, Lucinda Bateman, Jennifer Bland, Charles Lapp, Wendy Springs, Richard Podell, Trisha Fitzpatrick, Daniel Peterson, and Marco Maynard; Institute for Neuro Immune Medicine, Miami, Florida: Nancy Klimas, Elizabeth Balbin, Precious Leaks-Gutierrez, and Shuntae Parnell; and Mount Sinai Beth Israel, New York, New York: Benjamin Natelson and Diana Vu.
The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.
Manshu Yang (MY) and San Keller (SK) were supported by a National Institutes of Health (NIH) Grant Award (U2CCA186878). Jin-Mann S. Lin (JML) was supported by the Centers for Disease Control and Prevention (CDC).
Compliance with ethical standards
Conflict of interest
The authors declare no conflict of interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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