Validation of the extended e-health literacy scale: structural validity, construct validity and measurement invariance.

Background: Given the rapid proliferation and use of online health resources, many of which may be of dubious quality, there is an increasing need to develop electronic health literacy (e-health literacy) skills among the population of internet users. E-health literacy encompasses the skills and abilities needed to access, understand, validate, evaluate, interpret, and apply online health-related information. Measuring e-health literacy has become crucial for developing targeted interventions, assessing their impact, and producing high-quality research findings that can inform health policy and clinical practice, which can lead to improved health outcomes and potentially reducing health inequalities. The scales need to be valid and reliable so that decisions are based on high-quality data. In this regard, the issue of the measurement invariance of scales across different demographic groups has been neglected. This is critical, as assessments should be valid across different sociodemographic groups to avoid bias when comparing them. The aim of this study was to validate the Extended e-health literacy scale (eHEALS-E) on general population and investigate its structural validity and internal consistency, construct validity in terms of convergent and discriminant validity, and examine its measurement invariance across gender, age, education and social status.

Methods: The data were collected as a part of a national health literacy survey conducted by the Slovenian National Institute of Public Health. For this survey the initial eHEALS-E scale was revised in order to address its limitations and applicability to general population. Based on a nationally representative sample, the final sample for the analysis comprised 1,944 individuals who at least occasionally used one of the various internet services to obtain health-related information. Multiple group confirmatory factor analysis was used to examine the measurement invariance of the scale.

Results: With some adjustments, the measurement model of the revised 6-dimensional eHEALS-E scale demonstrated a good fit to the data (χ = 2508, df = 282, RMSEA = 0.064, SRMR = 0.070, CFI = 0.90). The scale had good internal consistency (alpha = 0.89). Although evidence of the scale's convergent and discriminant validity was partially provided, the analysis revealed robust measurement invariance across sociodemographic groups.

Conclusions: With a minor limitation, the scale ensures an unbiased e-health literacy assessment across different social groups, which is crucial for interventions that aim to reduce health-related social inequalities. This ensures that the interventions derived from the assessment of reality are equally valid and effective for everyone, regardless of their sociodemographic background.