Development and initial content validation of the Vienna post-exertional malaise questionnaire: an iterative mixed-methods study
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Published on: April 23, 2014
Theresa Pimminger1, Annika Ahrens-Schwabe2, Tobias Fragner1
1Center for Public Health, Department of Social and Preventive Medicine, Medical University of Vienna, Kinderspitalgasse 15, Vienna, 1090, Austria.
Objectives:
Post-exertional malaise (PEM) is a multidimensional exertion-response pattern involving diverse triggers, variable onset, and prolonged recovery. This study developed and content-validated the Vienna Post-Exertional Malaise (VPEM) Questionnaire, a patient-reported outcome measure assessing functional decline, recovery, crash-associated symptoms, and pacing adaptations in ME/CFS.
Methods:
An iterative mixed-methods instrument-development study combined quantitative ratings and qualitative feedback across sequential evaluation cycles. An initial 13-item draft, informed by existing PEM, fatigue, and functional-capacity instruments and consensus literature, was evaluated by individuals with ME/CFS or Post-COVID-19 syndrome (PCS) using Likert ratings, open-ended feedback, and interviews. Quantitative data were summarised descriptively, and qualitative data were analysed using deductive-inductive structuring content analysis. Revisions were documented in revision matrices. The revised instrument was evaluated by an interdisciplinary expert panel using domain-level and item-level ratings of relevance and clarity.
Results:
Twelve individuals with ME/CFS and one individual with PCS fulfilling ME/CFS criteria evaluated the questionnaire. Ratings showed high approval for length (92.3%) and terminology (76.9%), while completeness and clarity were more heterogeneous. Qualitative findings identified ambiguities in distinguishing PEM from non-specific fatigue, missing trigger domains, and insufficient representation of intra-individual variability. After revision, the expert panel (n = 11) rated PEM coverage as complete or largely complete (100%) and the multidimensional structure as suitable or very suitable (90.9%). Item-level ratings showed high relevance (S-CVI/Ave = 0.96), whereas clarity ratings were more variable (S-CVI/Ave = 0.82).
Conclusions:
The VPEM Questionnaire operationalises PEM as multidimensional post-exertional deterioration. Findings support initial content and face validity, warranting further psychometric validation.
