Abstract
BackgroundLittle attention has been paid to customising fatigue questionnaires for patients with Substance Use Disorders (SUDs). The present study aims to validate and shorten the nine-item Fatigue Severity Scale (FSS-9) and Visual Analogue Fatigue Scale (VAFS) for use with this population.MethodsWe used data from a nested cohort with annual health assessments with responses on the FSS-9 and VAFS. During the period 2016–2020, 917 health assessments were collected from 655 patients with SUD in Bergen and Stavanger, Norway. A total of 225 patients answered the health assessment at least twice. We defined baseline as the first annual health assessment when the health assessments were sorted chronologically per patient. We checked for internal consistency, and we used longitudinal confirmatory factor analysis (CFA) and linear mixed model (LMM) analysis to validate and shorten the FSS-9 and VAFS.ResultsThe internal consistency of the FSS-9 was excellent with a Cronbach’s α of 0.94 at baseline and 0.93 at the second annual health assessment. When shortening the FSS-9 to a three-item FSS (FSS-3, items 5–7), the Cronbach’s α was 0.87 at baseline and 0.84 at the second health assessment. The internal consistency was not affected when the VAFS was added to the FSS-3 and the FSS-9. The longitudinal CFA model showed a well-fitting model for the FSS-3 (χ2 = 13.33, degree of freedom = 8, P = 0.101). The LMM analysis showed equal linear changes at the individual level for the FSS-3 (slope: 0.00, P > 0.05) and FSS-9 (slope: 0.01, P > 0.05) between the health assessments.ConclusionThe FSS-9 could be shortened to the FSS-3 with high validity and reliability for patients with SUDs and the addition of VAFS did not provide much added variability.
Highlights
Little attention has been paid to customising fatigue questionnaires for patients with Substance Use Disorders (SUDs)
To ensure high-quality clinical trials focusing on fatigue, developing a validated and customized fatigue questionnaire aimed for Substance use disorder (SUD) patients is of particular interest
The present study shows that the Nine-item Fatigue Severity Scale (FSS-9) can be shortened to the Three-item Fatigue Severity Scale (FSS-3), with most of the included variance and validity retained
Summary
Little attention has been paid to customising fatigue questionnaires for patients with Substance Use Disorders (SUDs). Patients with SUDs often live in a chaotic situation with extensive medical and psychosocial health challenges, including polysubstance use, substance intoxications and withdrawals, psychiatric comorbidities (e.g., attention deficit hyperactivity disorder, psychosis disorders, or personality disorders), chronic viral hepatitis, financial risk, and temporary living situations [7, 8]. This might make surveying fatigue with questionnaires challenging and might influence the patients’ fatigue experiences and how they respond to questionnaires [9,10,11]. Using simple wording and phrases, avoiding the use of questions which differ in subtle ways which make them appear repetitive, and administering measures that produce reliable and valid scores based on very few questions, might be essential to ensuring reliable results in clinical trials on fatigue in this population
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