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Portuguese Version of the Intentional Non-Adherence Scale: Validation in a Population of Chronic Pain Patients

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Rute Sampaio, Mariana Cruz, Simão Pinho, Cláudia Camila Dias, John Weinman, José M. Castro Lopes

Original languageEnglish
Article number681378
JournalFrontiers in Pharmacology
Published19 Jul 2021

Bibliographical note

Funding Information: We acknowledge the patients in this study and all healthcare professionals at the participating chronic pain clinics. We are also deeply grateful to the panel of experts who worked with us on the consensus version of the instrument: Carina Raposo, Jos? Rom?o, Lu?s Filipe Azevedo, and Rosa Fragoso. Publisher Copyright: © Copyright © 2021 Sampaio, Cruz, Pinho, Dias, Weinman and Castro Lopes. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

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Objective: Despite the effectiveness of pain medicines, nonadherence to prescribed medication remains a major problem faced by healthcare systems. The aim of present study was to perform the translation, cultural adaptation, and validation of the Intentional Non-Adherence Scale (INAS) for the European Portuguese language in a sample of chronic pain patients. Methods: A Portuguese version of the INAS scale was constructed through a process of translation, back translation, and expert’s panel evaluation. A total of 133 chronic pain patients were selected from two chronic pain clinics from tertiary hospitals in Porto, Portugal. The protocol interview included the assessment of pain beliefs (PBPI), beliefs about medicine (BMQ), medication adherence (MARS-P9), and two direct questions about adherence previously validated. Results: The internal consistency in all subscales was α = 0.902 for testing treatment; α = 0.930 for mistrust treatment; α = 0.917 for resisting treatment; and α = 0.889 for resisting illness. Exploratory and confirmatory factor analysis revealed a four-factor structure that explained 74% of the variance. The construct validity of the INAS was shown to be adequate, with the majority of the previously defined hypotheses regarding intercorrelations with other measures confirmed. Conclusion: The Portuguese version of INAS could be a valuable and available instrument for Portuguese researchers and clinicians to assess the intentional nonadherence determinants during the management of chronic pain.

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