Santos, OsvaldoStefanovska-Petkovska, MiodragaVirgolino, AnaMiranda, Ana CristinaCosta, JoanaFernandes, ElisabeteCardoso, SusanaCarneiro, António Vaz2021-03-112021-03-112021Santos, O.; Stefanovska-Petkovska,M.; Virgolino,A.; Miranda, A.C.; Costa, J.; Fernandes, E.; Cardoso, S.; Vaz Carneiro, A. Functional Health Literacy: Psychometric Properties of the Newest Vital Sign for Portuguese Adolescents (NVS-PTeen). Nutrients 2021, 13, 790. https://doi.org/ 10.3390/nu130307902072-6643http://hdl.handle.net/10400.8/5480Self-management of health requires skills to obtain, process, understand, and use healthrelated information. Assessment of adolescents’ functional health literacy requires valid, reliable,and low-burden tools. The main objective of this study was to adapt and study the psychometric properties of the Newest Vital Sign for the Portuguese adolescents’ population (NVS-PTeen). Classic psychometric indicators of reliability and validity were combined with item response theory (IRT) analyses in a cross-sectional survey, complemented with a 3-month test-retest assessment. The NVSPTeen was self-administered to students enrolled in grades 8 to 12 (12 to 17 years old) in a school setting. Overall, 386 students (191 girls) from 16 classes of the same school participated in the study (mean age = 14.5; SD = 1.5). Internal reliability of the NVS-PTeen was = 0.60. The NVS-PTeen total score was positively and significantly correlated with Portuguese (r = 0.28) and mathematics scores (r = 0.31), school years (r = 0.31), and age (r = 0.19). Similar to the original scale (for the U.S.), the NVSPTeen is composed of two dimensions, reading-related literacy and numeracy. Temporal reliability is adequate, though with a learning effect. IRT analyses revealed differences in difficulty and discriminative capacity among items, all with adequate outfit and infit values. Results showed that the NVS-PTeen is valid and reliable, sensible to inter-individual educational differences, and adequate for regular screening of functional health literacy in adolescents.engFunctional health literacyQuestionairePsychometricsItem response theoryAdolescentsjournal articledoi:10.3390/nu13030790