title: [Instrument to measure adherence in hypertensive patients: contribution of Item Response Theory].
abstract: OBJECTIVE
  To analyze, by means of "Item Response Theory", an instrument to measure adherence to t treatment for hypertension.
  
  
  METHODS
  Analytical study with 406 hypertensive patients with associated complications seen in primary care in Fortaleza, CE, Northeastern Brazil, 2011 using "Item Response Theory". The stages were: dimensionality test, calibrating the items, processing data and creating a scale, analyzed using the gradual response model. A study of the dimensionality of the instrument was conducted by analyzing the polychoric correlation matrix and factor analysis of complete information. Multilog software was used to calibrate items and estimate the scores.
  
  
  RESULTS
  Items relating to drug therapy are the most directly related to adherence while those relating to drug-free therapy need to be reworked because they have less psychometric information and low discrimination. The independence of items, the small number of levels in the scale and low explained variance in the adjustment of the models show the main weaknesses of the instrument analyzed. The "Item Response Theory" proved to be a relevant analysis technique because it evaluated respondents for adherence to treatment for hypertension, the level of difficulty of the items and their ability to discriminate between individuals with different levels of adherence, which generates a greater amount of information.
  
  
  CONCLUSIONS
  The instrument analyzed is limited in measuring adherence to hypertension treatment, by analyzing the "Item Response Theory" of the item, and needs adjustment. The proper formulation of the items is important in order to accurately measure the desired latent trait.
authors.forename: Malvina Thaís Pacheco
authors.initials: MT
authors.lastname: Rodrigues
authors.forename: Thereza Maria Magalhaes
authors.initials: TM
authors.lastname: Moreira
authors.forename: Alexandre Meira de
authors.initials: AM
authors.lastname: Vasconcelos
authors.forename: Dalton Francisco de
authors.initials: DF
authors.lastname: Andrade
authors.forename: Daniele Braz da
authors.initials: DB
authors.lastname: Silva
authors.forename: Pedro Alberto
authors.initials: PA
authors.lastname: Barbetta
mesh_terms: D002138:Calibration; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000628:therapy*; D008297:Male; D055118:Medication Adherence; D008962:Models, Theoretical; D017063:Outcome Assessment, Health Care / Q000379:methods; D010349:Patient Compliance / Q000706:statistics & numerical data*; D011594:Psychometrics; D011795:Surveys and Questionnaires / Q000592:standards*