RESUMO
PURPOSE: This study aimed to simplify the version-1 Chinese and Western medication adherence scale for patients with chronic kidney disease (CKD) to a version-2 scale using item response theory (IRT) analyses, and to further evaluate the performance of the version-2 scale. MATERIALS AND METHODS: Firstly, we refined the version-1 scale using IRT analyses to examine the discrimination parameter (a), difficulty parameter (b) and maximum information function peak (Imax). The final scale refinement from version-1 to version-2 scale was also decided upon clinical considerations. Secondly, we analyzed the reliability and validity of version-2 scale using classical test theory (CTT), as well as difficulty, discrimination and Imax of version-1 and version-2 scale using IRT in order to conduct scale evaluation. RESULTS: For scale refinement, the 26-item version-1 scale was reduced to a 15-item version-2 scale after IRT analyses. For scale evaluation using CTT, internal consistency reliability (total Cronbach α = 0.842) and test-rest reliability (r = 0.909) of version-2 scale were desirable. Content validity indicated 3 components of knowledge, belief and behaviors. We found meritorious construct validity with 3 detected components as the same construct of medication knowledge (items 1-9), medication behavior (items 13-15), and medication belief (items 10-12) based upon exploratory factor analysis. The correlation between the version-2 scale and Morisky, Green and Levine scale (MGL scale) was weak (Pearson coefficient = 0.349). For scale evaluation with IRT, the findings showed enhanced discrimination and decreased difficulty of most retained items (items 1, 2, 3, 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 15), decreased Imax of items 1, 2, 3, 4, 6, 11, 14, as well as increased Imax of items 5, 7, 8, 9, 10, 12, 13, 14, 15 in the version-2 scale than in the version-1 scale. CONCLUSION: The original Chinese and Western medication adherence scale was refined to a 15-item version-2 scale after IRT analyses. The scale evaluation using CTT and IRT showed the version-2 scale had the desirable reliability, validity, discrimination, difficulty, and information providedoverall. Therefore, the version-2 scale is clinically feasible to assess the medication adherence of CKD patients.
RESUMO
OBJECTIVE: The self-reported scale is a widely used method to assess patients' medication adherence in clinical practice, but there is still a lack of medicine adherence measurement scale for patients with Chronic Kidney Disease (CKD). Therefore, this study aimed to develop a medication adherence measurement scale of traditional Chinese medicine and Western medicine, providing a tool for evaluating medicine adherence of CKD patients. METHODS: In the preliminary stage, we formed the prediction scale after three rounds Delphi method and it was filled by 20 patients, who were selected randomly. After pre-investigation and language adaption, we adjusted the prediction measurement scale which included 31 items based on Knowledge-Attitude-Belief Theory. Then, 222 CKD patients in Guangdong Hospital of traditional Chinese Medicine were investigated by this 31-item scale. We screened 31 items by Items analysis theory, including critical ratio, item correlation analysis, internal consistency analysis, principal component analysis and other methods. The left 26 items made up a formal scale. We collected and analyzed data of the 26-item scale and Chinese version of MGL scale, and took their scores correlation analysis as the criterion validity of the 26-item scale. At the same time, we evaluated content validity, Cronbach alpha coefficient and retest reliability of the 26-item scale. RESULTS: We developed a scale with 26 items and 5 dimensions finally. In the validation analysis, the scale had good construct validity and content validity. The Pearson relation index between respective scores of the scale and Chinese version of MGL scale was 0.426, P<0.01. The scale also had good reliability as its 0.915 in Cronbach alpha, 0.753 in retest reliability and P<0.01. CONCLUSION: The scale revealed great reliability and validity, which could be used as a measurement tool to evaluate the medication adherence of patients with CKD.