Validation of the eHealth Literacy Scale Instrument in a Restless Legs Syndrome Population: Classical Test Theory and Rasch Analysis Study.

Background: An increased use of the internet and digital health care for patients with long-term conditions implies a need for assuring digital health literacy skills. Patients with restless legs syndrome (RLS) represent a group where digital sources of information are highly valued. This is due to a difficult diagnosis and complex treatment situation that contributes to patients seeking out digital resources themselves to handle the perceived shortcomings in their care. To benefit from these resources, patients need to have the digital skills to explore information to optimize their understanding of the disease and its treatments. The eHealth Literacy Scale (eHEALS), which has been used in both general populations and patients with long-term conditions, could, if proven valid, be used by researchers and clinicians to assess digital health literacy among patients with RLS to inform the development of patient-centered digital health care information and interventions. Objective: The aim of the study is to investigate the psychometric properties of eHEALS in patients with RLS to determine its adequacy and potential utility. Methods: A cross-sectional design including patients with RLS from the Swedish national RLS patient organization was used. Data were collected via a mail-based survey comprising back-and-forth translated Swedish versions of the following instruments: eHEALS, Restless Legs Syndrome-6 Scale (RLS symptoms), Pittsburgh Sleep Quality Inventory (sleep quality), Epworth Sleepiness Scale (daytime sleepiness), Patient Health Questionnaire-9 (depressive symptoms), and CollaboRATE (shared decision-making). Confirmatory factor analysis and Rasch models were used to assess the validity and reliability of the eHEALS. Measurement invariance, unidimensionality, and differential item functioning across age, gender, medication use, sleep quality, level of depressive symptoms, and participation in care decisions were assessed. Results: A total of 788 patients with a mean age of 70.8 (SD 11.3) years participated. Among them, 64.7% (n=510) were women, 73.8% (n=582) were married or living together, and 43.5% (n=343) had attained a university education. A median eHEALS score of 28 (IQR 22-33) was reported. The unidimensionality of the eHEALS was supported by the confirmatory factor analysis and the Rasch model. The reliability of the eHEALS was confirmed using composite reliability and Cronbach α. No differential item functioning was identified for age, gender, medication use, shared decision-making condition, depressive symptoms, or sleep quality, meaning that these groups do not have different probabilities of endorsing a given item after controlling for the overall score. Conclusions: The eHEALS showed good validity and reliability and operated equivalently for men and women of different ages with various clinical and treatment conditions related to RLS. Accordingly, health care professionals can use eHEALS as a psychometrically sound tool to explore the digital health literacy level among patients with RLS.