Background
Despite increasing global attention to health literacy and adolescents’ digital health informationseeking, no unidimensional instruments measuring digital health literacy (DHL) in adolescents have reportedlybeen validated using Rasch modeling. Moreover, the evidence of adolescents’ abilities to navigate the health system(NAV-HL) in light of their DHL proficiency is still scarce. Therefore, our study aims to evaluate the psychometricproperties of a DHL instrument (HLS19-DIGI scale) in order to investigate DHL in adolescents and young adults aged16–25 and associations with abilities to navigate the health system.

Methods
A population-based cross-sectional survey among 890 Norwegian adolescents was conducted duringApril–October 2020 using computer-assisted telephone interviewing. Rasch modeling, independent samples t-test,chi-square test, and binary regression models were used to analyze the data.Results The HLS19-DIGI scale was sufficiently unidimensional, whereas no differential item functioning or disorderedresponse categories were observed. However, relatively poor targeting was revealed indicating too many easy itemsfor the target population. Yet, a high proportion (54%) of low DHL proficiency in adolescents was observed, as well asDHL was positively associated with the abilities to navigate the health system.

Conclusions
The HLS19-DIGI scale is considered a sufficiently unidimensional and valid instrument for measuringDHL in adolescents, which may be a useful tool for health authorities, public health workers, and health serviceproviders. While DHL affects adolescents’ abilities to navigate the health system, future research should measure andexamine their ability to utilize digital health services, separately.