Knowledge of phosphate control
Knowledge of phosphate control was measured by the Phosphate Control Knowledge Scale, which was a researcher-made tool. This questionnaire was developed by adapting the tools of similar studies and scientific recourses [This tool has 16 items with the answers “true” (1 point), “false” (0 points), and “I don’t know” (0 points). Items 1, 9, 10, and 13 were scored in reverse. The higher the score, the greater the Knowledge of phosphate control. This scale’s minimum and maximum scores are 0 and 16, respectively (Table Phosphate control knowledge scaleTo check the validity of the Phosphate Control Knowledge Scale, it was submitted for review to 10 faculty members of Shahid Beheshti University of Medical Sciences. During this process, in addition to qualitative content validity assessment, the necessity of the questions and their relevance to the research objectives were also evaluated based on Content Validity Ratio (CVR) and Content Validity Index (CVI), respectively [The reliability of this tool was established by test–retest and intra-class correlation calculation based on the responses of 10 participants who filled out the questionnaire two times with a 10-day interval. Using this method, the intra-class correlation coefficient was calculated to 0.75. The Cronbach’s alpha of the tool based on the responses of 20 HPs who were not included in the study was calculated to 0.88 that showed the instrument was reliable [