Background & Aims
Chronic pain (CP) significantly impacts daily functioning (1). This is particularly evident in hypermobile Ehlers-Danlos Syndrome and Hypermobility Spectrum Disorders (hEDS/HSD), conditions characterized by moderate-to-severe pain and joint hypermobility (2-3). These symptoms can be severe, leading to reduced employment, physical activity, social participation, and lower quality of life (3-6). The frequent injuries and pain in hEDS/HSD often result in pain-related fear, further exacerbating disability (3). The Tampa Scale of Kinesiophobia (TSK) and its variants (e.g., shortened 11-item TSK) are the most commonly used measures of pain-related fear of movement (7,8). A 2-factor version of the TSK-11 has been confirmed in mixed-CP samples (9). While the TSKs are often used with hEDS/HSD patients, they have not been validated for this group. We employed Rasch analysis to (i) validate the TSK-11 in hEDS/HSD, (ii) assess possible score biases, and (iii) offer solutions to address any bias.
Methods
This is a retrospective analysis of secondary data from a cross-sectional internet-based survey of adults (18-80 years old) with hEDS/HSD (n = 168) and pain-free participants (n = 108 [10]). Data was collected between March 2021- June 2021. Participant recruitment was promoted through patient partners (i.e., EDS-Canada, The ILC Foundation, EDS-specific Facebook groups), experts in the field, and Amazon Mechanical Turk (Mturk). Rasch analysis, a robust psychometric approach, was used to evaluate (i) overall model fit unidimensionality, (ii) Guttman scaling (i.e., evaluating for disordered thresholds), and (iii) reliability of the resulting fit statistics. An iterative approach to testing and exploring corrections was employed to optimize model fit. Potential scoring biases were also assessed, by considering differential item function.
Results
The analyses indicated that there was good distribution of responses at each level of the scale for each item (range = 21 – 119); this supports the absence of floor or ceiling effects. Systematic differences in item scoring were found for gender, diagnosis, and pain severity (e.g. pain-free participants’ responses to item 1 about fear of injury were systematically different than those with hEDS or HSD). The aforementioned 2-factor version of the TSK-11, comprised of a somatic subscale (items 3-6, 8) and an activity avoidance subscale (items 1, 2, 7, 9-11), did not fit Rasch model with this sample. Instead, model fit was achieved by clustering ‘thoughts about exercise’ items (1, 9, 11) and ‘hypervigilance and risk’ items (2-8, 10). However, fit issues were only fully resolved when persons identifying as transgender (n=4) were removed from the sample. Cronbach’s alpha for the final model was acceptable at 0.76.
Conclusions
The current study confirms the validity of the TSK-11 for use in patients with hEDS/HSD. However, the original two subscales of the TSK-11 were not corroborated by Rasch analysis with this novel clinical sample. Two new item sets, (i) Thoughts about Exercise and (ii) Hypervigilance and Risk, are proposed. Scoring biases based on personal or clinical characteristics were found for certain items on the TSK-11, indicating opportunities for correction to improve precision when used in research. Our finding that responses from persons identifying as transgender added unpredictable variability warrants further exploration, as does the systematic differences in responses from person with hEDS and HSD. Qualitative interviews with individuals with hEDS/HSD to explore their appraisals for TSK-11 items may help to address bias and tailor this tool for this complex pain population.
References
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