Objective: To elaborate and validate an instrument of adherence to treatment for systemic arterial hypertension, based on Item Response Theory.
Methods: The process of developing this instrument involved theoretical, empirical and analytical procedures. The theoretical procedures included defining the construct of adherence to systemic arterial hypertension treatment, identifying areas involved and preparing the instrument. The instrument underwent semantic and conceptual analysis by experts. The empirical procedure involved the application of the instrument to 1,000 users with systemic arterial hypertension treated at a referral center in Fortaleza, CE, Northeastern Brazil, in 2012.. The analytical phase validated the instrument through psychometric analysis and statistical procedures. The Item Response Theory model used in the analysis was the Samejima Gradual Response model.
Results: Twelve of the 23 items of the original instrument were calibrated and remained in the final version. Cronbach's alpha coefficient (α) was 0.81. Items related to the use of medication when presenting symptoms and the use of fat showed good performance as they were more capable of discriminating individuals who adhered to treatment. To ever stop taking the medication and the consumption of white meat showed less power of discrimination. Items related to physical exercise and routinely following the non-pharmacological treatment had most difficulty to respond. The instrument was more suitable for measuring low adherence to hypertension treatment than high.
Conclusions: The instrument proved to be an adequate tool to assess adherence to treatment for systemic arterial hypertension since it manages to differentiate individuals with high from those with low adherence. Its use could facilitate the identification and verification of compliance to prescribed therapy, besides allowing the establishment of goals to be achieved.