1. Overview of the study
A cross-sectional analytical survey was conducted from September 2023 to January 2024. This study was performed in Labbafinejad hospital, Tehran, Iran. A questionnaire assessed patients' knowledge, attitude, and performance toward CKD treatment. Finally, the medical adherence of the patients was evaluated by the Morisky medication adherence scale (MMAS) (22).
2. Sample size
G-Power software was used to estimate the sample size. With an effect size of 0.25, 0.05 margin of error, and 80% power and a 10% non-response rate, the sample size calculated as 105 patients`.
3. Inclusion and exclusion
According to NKF KDOQI clinical practice guideline (23), the inclusion criteria were patients with CKD and GFR < 60 mL/min/1.73 m2. Patients who did not tend to give their personal information or did not meet the inclusion criteria were excluded from the study.
4. Data collection and clinical consultation
We informed the patients about the study process and explained how to complete the questionnaire in the first step. In addition, to collect data through the questionnaire, we gathered the patients` medical history and previous medicine consumption. After data collection, medical consultation services were provided by a clinical pharmacist. A questionnaire was conducted to evaluate the CKD patients' knowledge, attitude, and performance. After extracting the main criteria of the subject by searching texts and interviewing experts, the questionnaire was structured. To confirm internal consistency, Cronbach's alpha was calculated. The questionnaire showed an acceptable internal consistency with the Cronbach's alpha of 0.706.
The questionnaire was divided into five parts. Patients' demographic information was asked, including age, height, weight, lean body weight (LBW), body mass index (BMI), gender, occupation, education, geographic area, marriage status, and the number of drugs consumed per day in the first section. The second section assessed the patients' knowledge about CKD by nine (two options: correct, incorrect) items. In the third section, the attitude of the patients toward CKD was evaluated by 17 items. The attitude section was designed in a five-point response scale (strongly agree, agree, not sure, disagree, and strongly disagree).
To evaluate the performance, patients were scored in eight items. The score of responses was ranged from one to five. To determine patient adherence, MMAS was used. In the first seven questions, each negative response and each positive response is given one and zero point, respectively, except for the fifth question in which the scoring process is inverse. The last question has five scales (0, 0.25, 0.5, 0.75, and 1). The final scores are classified as poor (less than 6), average (6–8), and high (more than 8) adherence.
5. Statistical analysis
Finally, collected data were analyzed using SPSS v.25 software. Descriptive results were reported using frequency, mean ± standard deviation (SD). To check the parametricity of the data, the Kolmogorov-Smirnov test was used. Paired T-test was used to compare the subgroup outcomes. Kruskal-Wallis and Mann-Whitney tests were used to compare non-parametric data.