Desenvolvimento de um instrumento para avaliação da adesão à farmacoterapia com varfarina.

Abstract

The warfarin is recommended for primary and secondary thromboprophylaxis in different clinical conditions. It's a drug with narrow therapeutic index and predisposition to adverse events, which may be a consequence of medication non-adherence. Adherence can encompass health-related behaviors in addition to medication administration. Its assessment is relevant in the pursuit of treatment goals and prevention of complications. Adherence assessment can be performed properly using validated and treatment-appropriate measurement scales. The objective of the present study was to develop an instrument to assess adherence to warfarin therapy. This estudy was divided into three stages, namely: 1) Elaboration of a protocol to carry out a systematic review of the literature; registered in the International prospective register of systematic (PROSPERO), under code CRD42019128324, 2) Systematic review to investigate validated instruments used to assess adherence to warfarin therapy; 3) Development of the instrument "Tool to assess adherence to warfarin therapy". Observational and experimental studies were searched in the MEDLINE (PubMed), LILACS, EMBASE and Cochrane Library databases. Inclusion criteria: participants of ≥18 years of age, from both sexes, on chronic anticoagulation with warfarin and the use of validated instruments to assess adherence to warfarin therapy. Two reviewers performed the independent search and discrepancies were resolved by a third reviewer. The tool was designed considering the medication administration and treatment-related dimensions. The development of the instrument comprised: i) construction of a conceptual map; ii) proposal of a preliminary version of the tool; iii) content analysis by experts; and iv) semantic analysis through a pre-test. Nineteen articles were selected for the review, including 17 cross-sectional studies, a cohort study and a quasi-experimental study, published in 2009-2019. Of the 35 items developed for the tool, 14 were discarded and 19 were modified, resulting in 21 items covering the following dimensions: intake of warfarin pills (n=10), self-care associated with the use of warfarin (n=7) and health monitoring (n=4). The tool showed adequate content validity, as well as good acceptance and understanding of the items by patients. The theoretical framework resulting from the systematic review was useful for the different stages of instrument development. Furthermore, the systematic review highlighted a gap in knowledge, the scarcity of validated instruments to assess adherence to warfarin therapy. Limitations were found in instruments as the assessment of the isolated use of medication and the lack of analysis of other relevant therapeutic aspects. More psychometric tests are needed to ensure the construct validity, reliability and stability of the instrument, which could be useful for a global assessment of adherence to warfarin therapy and planning strategies to improve safety and adherence to therapy.