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Rasch Analysis of the 7-Item Fatigue Severity Scale (FSS-7) in Traumatic Brain Injury
Frederik Have Dornonville de la Cour1, Tine Nielsen, Martin Matre
1Author Affiliations: Neurorehabilitation Research and Knowledge Centre, Copenhagen University Hospital-Rigshospitalet, Glostrup, Denmark (Dornonville de la Cour); Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark (Dornonville de la Cour); The Elsass Foundation, Charlottenlund, Denmark (Dornonville de la Cour); The Danish Center of Psychotraumatology, Department of Psychology, University of Southern Denmark, Odense, Denmark (Nielsen); Department of Applied Research in Education and Social Science, UCL University College, Odense, Denmark (Nielsen); Center for Research and Education, Sunnaas Rehabilitation Hospital, Bjørnemyr, Norway (Matre, Løvstad, and Løke); Department of Psychology, University of Oslo, Oslo, Norway (Matre and Løvstad); Department of Physical Medicine and Rehabilitation, Oslo University Hospital, Oslo, Norway (Andelic); and Institute of Health and Society, Center for Habilitation and Rehabilitation Models and Services (CHARM), University of Oslo, Oslo, Norway (Andelic).
The 6-item Fatigue Severity Scale (FSS-6) is a valid and reliable tool for measuring fatigue in traumatic brain injury (TBI) survivors. This revised scale offers improved accuracy for TBI rehabilitation and research.
Area of Science:
- Neuroscience
- Rehabilitation Medicine
- Psychometrics
Background:
- Fatigue is a common and persistent symptom following moderate-to-severe traumatic brain injury (TBI).
- Accurate measurement of fatigue is crucial for effective TBI rehabilitation and research.
- The Norwegian 7-item Fatigue Severity Scale (FSS-7) has been used, but its psychometric properties in TBI populations require evaluation.
Purpose of the Study:
- To assess the validity, reliability, and targeting of the Norwegian 7-item Fatigue Severity Scale (FSS-7) in adults with moderate-to-severe TBI.
- To identify potential modifications to improve the scale's performance in this population.
Main Methods:
- Secondary analysis of longitudinal data from 94 TBI patients (mean age 45.8 years) at 6 and 12 months post-injury.
- Utilized Rasch modeling and graphical log-linear Rasch models (GLLRM) to evaluate the FSS-7.
- Examined differential item functioning (DIF) for sex, age, education, and sleep disturbances.
Main Results:
- The FSS-7 did not fit the Rasch model; however, a 6-item version (FSS-6) excluding item 4 demonstrated good fit to a GLLRM.
- The FSS-6 exhibited excellent reliability (r = 0.936) and no detected DIF or item parameter drift over time.
- Targeting of the FSS-6 was suboptimal, reaching only 57% of maximum test information on average.
Conclusions:
- The FSS-6 is a valid and highly reliable measure of fatigue in adults 6 and 12 months post-TBI.
- The FSS-6 score is invariant across demographic and sleep-related variables, making it suitable for screening and monitoring fatigue in TBI.
- Further research with larger, diverse TBI samples is recommended to improve the targeting of the FSS-6.
