Psychometric properties of a COVID-19 health literacy scale in a sample of German school principals applying Rasch analysis

Background: During the COVID-19 pandemic, health literacy was found to be an asset to manage health-related information. The HLS-COVID-Q22 has been developed to measure COVID-19 health literacy. External validation needs to be assessed in different populations to verify the questionnaire’s functioning. The present study aimed to evaluate the psychometric properties of the HLS-COVID-Q22 in a sample of German school principals. Methods: The sample consisted of 2187 German school principals who completed the HLS-COVID-Q22 online from April to March 2021. The data was analyzed using Rasch analysis, applying the Partial Credit Model for polytomous data. Dimensionality, item fit statistics and rating scale functioning was tested. Values for item difficulty and person ability as well as reliability indices were computed. Results: Unidimensionality could be confirmed. The rating scale categories worked as intended, participants used every rating step category. Generally, item fit was verified. One item showed potential misfit but could remain in the questionnaire as excluding the item did not reduce reliability. A person separation index of 3.41 and person reliability of 0.92 showed excellent differentiation between COVID-19 health literacy levels. Furthermore, the values for item separation of 20.08 and item reliability of 1.0 indicate good construct validity. Conclusions: The German version of the HLS-COVID-Q22 appears to be a reliable measurement tool for the target population. Evidence for construct, statistical and fit validity was collected. Future studies need to test additional types of validity like convergent and divergent validity to further evaluate the questionnaire. Moreover, the psychometric properties of the translated versions of the HLS-COVID-Q22 should be compared using Rasch analysis.