Data collection and analysis
P‐value
Data were analysed using SPSS software 19.0. First, the demographic variables in the two groups were compared by Chi‐Square and T‐test. Then, the Kolmogorov–Smirnov test was performed to determine the normality of scores. Its results revealed the normal distribution of all scores. Subsequently, the results were analysed by the independent samples T‐test and repeated measures at different stages. Independent samples T‐test was used to compare the mean scores of adherence and self‐efficacy between the intervention and control group. The repeated measures analysis of variance was used to assess the effect of motivational interviewing on adherence and self‐efficacy in patients in each group. Marginal model with Generalized Estimating Equation (GEE) approach applied for controlling of potential confounders. A P‐value of <0.05 was considered as statistically significant.