Effectiveness of Combining Patient Follow-Up With an Educational Intervention on Self-Management Skills of Type 2 Diabetes Mellitus Patients: A Controlled Intervention Study in Primary Care

For use in the clinicaltrials.gov registration of this clinical trial, a comprehensive "Detailed Description" text-which does not contradict the "Brief Summary" section or repeat the information contained therein and which includes the technical and scientific background-has been prepared below:

1. Scientific Rationale and Background The prevalence of diabetes is rapidly increasing worldwide; according to data from the International Diabetes Atlas 2025, an estimated 588.7 million people aged 20-79 have diabetes, and this number is expected to reach 822.5 million by 2050. The TURDEP-2 study conducted across Turkey also revealed a similar upward trend, showing that the prevalence of diabetes rose from 7.2% to 13.7% over a 12-year period (1998-2010). The long-term microvascular and macrovascular complications of diabetes constitute a significant disease burden; for example, diabetic nephropathy-the most common cause of end-stage renal disease in developed countries-develops in 20-40% of people with Type 2 Diabetes (T2DM) and increases the risk of cardiovascular mortality. Additionally, diabetic neuropathy-characterized by symmetrical loss of sensation-and peripheral vascular disease are the primary causes of foot ulcers and form the basis of diabetic foot cases, leading to approximately 12,000 amputations annually across Turkey.

   Primary care providers are responsible for regularly monitoring patients with diabetes, recommending screenings for complications, and educating patients on how to protect themselves from these complications. However, effective control of the disease requires patients to take responsibility for managing their own condition (self-management). Individuals with low health literacy (HL) have a higher risk of developing diabetes complications (particularly neurovascular complications and retinopathy), and these patients are less likely to have sufficient knowledge about diabetes care and self-care activities. According to data from the Turkey Health Literacy Survey, 24.5% of the population has inadequate health literacy, while 40.1% has problematic health literacy. Although there are many educational programs in the literature aimed at supporting diabetes self-management, the majority of these studies have been conducted in secondary or tertiary care facilities or specialized diabetes centers; however, access to such multidisciplinary expert teams is quite limited in communities with scarce resources. Therefore, there is a need for structured intervention models that can be implemented at the primary care level, aim to improve self-management skills even among patients with low health literacy, and are based on physician-patient collaboration.

2. Study Design and Sample Size This study was designed as a pre-test/post-test comparative, non-randomized controlled clinical trial. The study was conducted at three different primary care centers in Istanbul. Instead of randomization, center-based grouping was chosen; patients registered at ASM-A formed the intervention group (IG), while those registered at ASM-B and ASM-C formed the control group (CG). This design was chosen to prevent patients at the same center from interacting with one another and sharing information (the contamination effect).

   The study's sample size was calculated using the Clinical Sample Size Calculator (ClinCalc) program, targeting a minimum increase of 8 points in self-management scale scores in the intervention group following the intervention, at a 95% confidence level and 80% power. Accordingly, with a 1:1 ratio, at least 40 participants were planned for each group, and the study was completed with a total of 84 patients.

3. Theoretical Framework of the Intervention (Theoretical Framework of the Intervention) In educating patients with low health literacy, evidence-based strategies such as using simple language, focusing on direct actions, limiting the number of messages, taking cultural differences into account, supporting instructions with visual aids, and continuously monitoring the patient's level of understanding (teach-back method) have been adopted. Developed in line with these principles, the "Diabetes (DM) ID Card" and "DM Diary" have been visually enriched and prepared in extremely simple language to enable patients to manage their own self-care without being overwhelmed by complex medical information.

   Instead of conducting a traditional, one-way educational session, an interactive follow-up model was implemented in which the physician and patient engage in a two-way dialogue, and the patient actively shares their habits and the challenges they face. During this process, patients received in-person training from their physicians on how to perform daily blood glucose monitoring and self-examinations of their feet.

4. Data Collection Tools and Scales (Measurement Instruments)

   Data from participants were collected using the following valid and reliable instruments administered by family physicians at the initial visit and at the end of the third month:

   Sociodemographic Questionnaire: A form prepared by the researchers that asks patients about their age, gender, education, income level, smoking and alcohol habits, and comorbidities.

   Hacettepe University Adult Health Literacy Scale Short Form (HU-SOÖ): A 24-item measure with two dimensions-Health Literacy and Self-Efficacy-and a Cronbach's alpha value of 0.84. The scale does not have a specific cut-off point; higher scores indicate a higher level of health literacy.

   Type 2 Diabetes Self-Management Scale (DÖYÖ): A 19-item scale using a 5-point Likert scale with a Cronbach's alpha value of 0.86. The scale consists of three subscales: "Healthy Lifestyle Behaviors," "Blood Sugar Management," and "Use of Health Services."

5. Statistical Analysis Plan All data obtained in this study were analyzed using IBM SPSS version 23.0. Categorical variables were described using frequencies and percentages; the distribution of continuous variables was assessed using the Kolmogorov-Smirnov test and by examining kurtosis and skewness values. The chi-square and McNemar tests were used for categorical comparisons between groups. In the analysis of continuous variables, the paired t-test and independent samples t-test were used for data showing a normal distribution; for data not normally distributed, the Wilcoxon signed-rank test was preferred. Correlations between variables were calculated using Pearson or Spearman tests.

   An intent-to-treat (ITT) analysis was applied to control for the effect of patients who were lost to follow-up on the analysis. In this context, the post-test scores of 5 patients from each group who were unable to attend follow-up visits for various reasons (unreachability or death) were included in the analysis without assuming any change (while retaining their baseline scores).

6. Ethical Approval and Permissions (Ethical Approvals) The ethical compliance of the study was approved by the Marmara University Faculty of Medicine Clinical Research Ethics Committee on May 7, 2021 (Protocol Code: 09.2021.601). Additionally, an official research permit (No. 2021/44) was obtained from the Istanbul Provincial Health Directorate on October 11, 2021.