title: [Are there valid instruments? A necessary debate].
authors.affiliation: Universidad Privada del Norte, Lima, Perú. Electronic address: jventuraleon@gmail.com.
authors.forename: José Luis
authors.initials: JL
authors.lastname: Ventura-León
mesh_terms: D006801:Humans; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires