A regular LINE OA was first set up to explore its basic functionalities, applying two functions aligned with 3 DDEF digital strategies: (1) chat: “Digital Feedback” and “Digital Communication,” and (2) multimedia and multipage messages: “Digital Education.” For example, CKD-related information (eg, symptoms, staging, and risk factors) could be delivered through autoresponse messages triggered by specific keywords. However, such keyword-based use was inconvenient and insufficient for promoting lifestyle modification among CKD dyads, as prior medical applications of LINE OAs mainly focused on clinic operations (eg, appointment scheduling and reminders) rather than ongoing lifestyle support [24]. These limitations highlighted the need for integration with third-party application programming interface (API) plug-ins to enable more advanced functionalities.

AlleyPin Interactive Ltd Co is a LINE-certified Gold-level technical partner in the health care industry, providing API technical resources to meet diverse needs. Their cloud-based doctor-patient interaction management system, “DoctorConnect 1.Talk,” when integrated with the team’s LINE OA, can provide more advanced and user-friendly functionalities, including (1) service menu setup: it allows up to 8 buttons with multilayered structures for resource integration, beyond the 6-button limit of LINE OA; (2) enhanced multimedia and multipage messages: multiple buttons can be set within a single message, enabling users to access tailored health information via menu clicks without manual text input; and (3) case tracking system: it supports member management, scheduled “Push” messages, and interaction through AlleyPin’s independent backend.

The service menu content and layout were designed not only by following the DDEF but also in consultation with a health education nurse from a university-affiliated hospital and 2 nephrologists, ensuring the platform met clinical needs. Through the integration of LINE OA and AlleyPin Interactive’s API plug-in, our platform now effectively adopted 3 digital strategies—“Digital Education,” “Digital Feedback,” and “Digital Communication”—to support CKD dyads. To further apply the other 2 digital strategies—“Digital Monitoring” and “Digital Analysis,” an extended app was developed and integrated with the LINE OA in the next step.

After exploring various options and evaluating alternative platforms, the team discovered that Google’s AppSheet platform could effectively compensate for the current platform’s shortcomings and integrate with LINE OA. AppSheet is a platform for developing mobile and web apps that do not require programming code and can integrate with cloud spreadsheets or databases such as Google Drive and Office 365 as data sources [25]. The team immediately began developing the app prototype and conducted iterative testing.

As the digital platform was not selected during the development of DDEF, the team, after the platform selection and development process outlined in steps 1-3, reviewed the correspondence between the DDEF and the functions provided by this integrated digital platform. Based on this, interventions were designed to promote lifestyle modification for CKD dyads.

After establishing our digital platform prototype, the team invited 10 early-stage CKD (stages 1-3) dyads receiving regular treatment at a university hospital to use the platform in their daily lives. Besides assisting dyads in installing the digital platform on their smartphones, a user manual (Multimedia Appendix 1) was provided for each dyad to learn the operations at home. At the time of enrollment, operational instructions for various functions were provided by a research assistant (CYH) according to the manual.

A user feedback form (Multimedia Appendix 2) was provided to be filled out by the dyads at least 1 month apart during their next clinic visit. For each of the 6 major functions, the form assessed the following five elements: (1) interface clarity, (2) ease of operation, (3) acceptability: like or not, (4) intention to continue usage, and (5) satisfaction rating from 1 to 5 (Table 1). A brief interview was conducted with each dyad to obtain further feedback. The platform was iteratively optimized based on both system usage data and user feedback.

Our LINE OA acts as the main hub for real-time interaction with users via text or voice chat. Moreover, by clicking buttons from the service menu (Figure 2A), users can access various resources for CKD management, retrieved or adapted from the official websites of Taiwan Society of Nephrology and Taiwan Kidney Foundation. The eight buttons featured on the service menu were introduced: (1) Health Education Information: providing basic kidney disease knowledge, evaluating kidney function, dietary and exercise guidelines, and so on (Figure 2B). (2) Kidney Support Teammate: multipage messages providing support resources for caregivers (SOs) (Figure 2C). (3) Frailty Section: providing health education information about frailty prevention and intervention. (4) Latest News: linking to the LINE OA’s post area, forwarding information about relevant hospital events. (5) Record Values: users can log self-measured physiological values, and the system records and generates reports for feedback. (6) Reminder Settings: users can log their next appointment dates, and reminders are scheduled through the AlleyPin Interactive backend. (7) Kidney Health Mission: encouraging daily completion of “Record Values” and “Kidney Health Diary” (recording daily diet, medication, and physical activity). (8) Inquiry & Consultation: providing answers to frequently asked questions for CKD management; a consultation channel is provided for further queries (Figure 2D).

Our extended app mainly interconnects with the functions of “Record Values,” “Reminder Settings,” and “Kidney Health Mission” provided by our LINE OA with API plug-ins. Users can directly access the corresponding pages of the extended app by clicking on LINE OA service menu buttons, with the specific paths as follows: (1) Clicking “Record Values” on LINE OA service menu jumps to the “New Entry” page of the extended app, where users can log blood pressure, heart rate, and weight, and optionally enter blood sugar or blood test report data (Figure 3A). (2) Clicking “Reminder Settings” → “Go to Reminder Setting Page” on LINE OA service menu jumps to the extended app to view the next appointment date and time, which users can update manually (Figure 3B). (3) Clicking “Kidney Health Mission” on LINE OA service menu allows users to perform 2 “Daily Tasks,” jump to the extended app to log physiological values or write a kidney health diary (recording daily diet, medication, and physical activity) (Figure 3C1). Alternatively, they can click “Challenge Missions” → “View Title Challenge Progress” on the extended app to confirm task execution status (Figure 3C2).

In addition to the functionality accessible via LINE, the extended app interface also has a bottom-placed menu with five buttons (Figure 3), each briefly described as follows: (1) My Entries: viewing the “Usage Report” (the page redirected after clicking “View Title Challenge Progress” on LINE), “Physiological Value View,” and “Blood Test Record” to check entered values. (2) Chart View: visualizing self-entered physiological values in graphical form. (3) New Entry: same as clicking “Record Values” on LINE OA. (4) Kidney Health Diary: adding, viewing, or editing written kidney health diaries. (5) Reminder Settings: same as clicking “Go to Reminder Setting Page” on LINE OA.

The data entered by users on various pages of the extended app were synchronized with their device IDs and sent back to the corresponding Google Sheets worksheets. Through these worksheets, the team can view all user-entered data and identify them based on the device ID and a custom user identification code. Subsequently, security filters were set up, distinguishing by device ID, enabling individual users on the front end (ie, extended app interfaces) to access only their entered data.

With the completion of the extended app’s development and integration with the LINE OA, it can now fully use the “Digital Monitoring” strategy to allow both the research team and the users to track physiological values, daily diet, medication, and physical activity. For the application of the “Digital Analysis” strategy, we calculate user metrics such as accumulated entry counts, entry activity rates (EARs), and consecutive entry days. These serve as reference indicators for users’ lifestyle modification progress, enabling personalized interventions through the LINE OA.

Referring to the DDEF, interventions delivered through our integrated digital platform were designed and finalized through the following three processes:

After consulting health care providers and observing practical scenarios, we confirmed the benefits of regular execution of the 2 daily tasks for both patients and health care providers. Recording physiological values generates easily readable reports, facilitating quick understanding of trends in physiological value changes. Writing a kidney health diary allows health care providers to confirm whether the patient’s meals align with the principles of a CKD diet, and it serves as a reminder for the patient to engage in physical activity and take medication correctly. Inappropriate medication check items reference the Chronic Kidney Disease Self-Care Scale [35] and the Elderly Medication Adherence Assessment [36], consolidated into 4 items: “missed medication,” “not taking medication on time,” “self-adjusted medication or dosage changes,” and “using nonprescribed medication.”

To implement the gamification strategy, the team needed to calculate the number of consecutive days a user completed daily tasks from today backward. With the assistance of generative artificial intelligence, ChatGPT, for syntax writing, we used Google Apps Script to execute custom functions to solve this issue. Furthermore, the team further simulated data using RStudio (Posit Software, PBC) and attempted to interpret it using Item Response Theory to link the 2 indicators, “consecutive days” and “entry activity rate.” The calculation method for the EAR is as follows:

The EAR can be viewed as an “ability” indicator for users performing daily tasks. A higher EAR indicates a more regular execution of daily tasks. The team simulated different levels of EARs (from 0% to 100%, at intervals of 5%) for 180 observation days, with or without task execution, a total of 10,000 times. The frequency of achieving various Kidney Health Titles was calculated among these 10,000 simulations (Table 4).

The simulation results provided item characteristic curve for each Kidney Health Title (Figure 4). These curves suggested that higher ability to perform daily tasks (indicated by a higher EAR) leads to a higher chance of achieving specific titles (indicated by more achievement instances). Using 5000 times of achievement as a baseline, its corresponding EAR on the item characteristic curve represents the difficulty level in achieving that specific Kidney Health Title. These results provide adequate rationality for the gamification strategy: assuming users in different stages of change have different EARs, this strategy sets appropriate challenges accordingly, aligning with our aim of providing corresponding interventions based on CKD dyads’ different motivational states.

After the initial prototype of our digital platform went live, 10 CKD dyads visiting nephrology clinics regularly at a university hospital were invited to participate in the trial use from August to October 2023. One of the SOs (no. 003S) was invited by the patient but did not decide to participate in the end, resulting in a total of 19 participants. All dyads completed the user feedback form and returned it during the next visit. Table 5 shows the basic demographics of the participants. The following sections separately analyzed (1) the LINE message activity, (2) usage of the extended app, and (3) dyadic feedback content.

Their scores regarding the compliance of various functions with usability principles were tallied, averaged, and summarized in Table 10. On average, the compliance scores for each principle ranged between 0 (partially complies) and 1 (complies). The functions’ average compliance with the 10 usability principles ranged from 89% to 93%. This suggests that the evaluators generally perceived that the digital platform’s various functions mostly complied with the usability principles.

The breakdown of issues raised by evaluators about each function’s incompliance with certain principles and their recommendations is as follows:

1. Health Education Information

2. Kidney Support Teammate

3. Record Values

4. Reminder Settings

5. Kidney Health Mission

6. Inquiry & Consultation

Overall, based on the evaluation scores and feedback from evaluators on each function of the digital platform concerning various principles, this phase successfully acquired specific recommendations for improving the platform’s usability. These suggestions can generally be categorized into three aspects: (1) enhancing user operation convenience, such as adding a return option in Health Education Information, Kidney Support Teammate, and Inquiry & Consultation, reducing repetitive operation hassles; (2) pushing more relevant and engaging information, for instance, pushing corresponding educational content based on user records; and (3) enhancing interactivity and feedback of functions, such as providing personalized memory functions for highly clicked content, warning after inputting abnormal physiological values, or providing feedback from professionals. Results of the heuristic evaluation have guided the modification of the digital platform for the next iteration to enhance user experience.

This section describes the designed task scenario for each function and summarizes participants’ general task performance as well as their ASQ ratings:

1. Health Education Information: The task scenario reflected the need for patients with CKD to calculate their estimated glomerular filtration rate (eGFR) independently. To accomplish this task, users can navigate through the Health Education Information section in our LINE OA to find a link to a web page with an eGFR calculator. Results indicated that 3 out of 5 dyads completed this task successfully (success rate 60%), with an average completion time of approximately 4.5 minutes. Operational errors were observed with numbers 002, 005, and 009, who navigated to the wrong sections, causing them additional time to locate the eGFR calculator. Another error occurred when number 007 could not find the box to enter the value of creatinine (CREA), as the enlarged font size setting obscured a clear presentation of the calculator elements on the smartphone. The average ASQ score for this task is 3.6, which is the lowest score among all tasks, indicating that dyads were the least satisfied with the ease and the time required for this task. They also perceived minimal help from the user manual.

2. Kidney Support Teammate: The task scenario involved an SO finding effective ways to support a patient who is attempting lifestyle modification. The Kidney Support Teammate in our LINE OA provides such information for SOs to implement supportive strategies. The task success rate is 80%, with only 1 dyad failing to complete this task. The average completion time exceeded 5 minutes, which is the longest among all tasks. All dyads took time to navigate different sections before they located the target information for this task. Dyads numbers 005 and 009 experienced uncertainty as they browsed through the correct section but did not recognize the target information. The average ASQ score is 4, indicating a moderate but relatively low level of user satisfaction compared with the other tasks.

3. Record Values: The task scenario reflects the need for patients with CKD to monitor their own physiological data. Completing this task requires the user to click “Record Values” on the service menu of our LINE OA or click “New Entry” on the extended app and input the numbers. The task success rate is 100%, with an average completion time of only 1 minute. Dyad number 007 encountered initial difficulty when trying to input the CREA value. The average ASQ score is 6.2, which is the highest among all tasks. These results suggested that this function is user-friendly and intuitive, leading to high user satisfaction.

4. Reminder Settings: The task scenario arises when patients with CKD wish to set a reminder for their upcoming clinical appointment. Dyads will need to input the date and time of their next appointment using the extended app and notify the research team via LINE OA to set an automatic message reminder. The task success rate is 100%, with an average completion time of around 2 minutes. Dyads numbers 002 and 007 seemed unfamiliar with this function as they clicked “New Entry” on the extended app, which redirected them to the wrong page. The average ASQ score is 4.9, indicating a moderate satisfaction level with this function.

5. Kidney Health Mission: The task scenario revolves around the essential practice of tracking daily diet, a key aspect of managing CKD. Users can access this task by clicking “Kidney Health Mission” on the service menu of our LINE OA or selecting “Kidney Health Diary” on the extended app to upload a photograph or text note regarding their diet. The task success rate is 100%, with an average completion time of just 1 minute. All dyads completed the task without encountering any operational errors, indicating that the design of this function is sufficiently intuitive. The average ASQ score is 5.8, demonstrating a relatively high level of satisfaction compared with the other tasks.

6. Inquiry & Consultation: This task scenario arises when patients with CKD encounter health-related inquiries at home without access to a health care professional. Users can explore the frequently asked question section in our LINE OA to seek answers to their questions. For instance, this task involves users wanting to learn about the symptoms of hypoglycemia (low blood sugar) using our platform. The task success rate is 80%, with dyad number 002 failing to complete the task. On average, it takes around 3 minutes to complete the task, as all dyads navigate through different sections of our LINE OA to find the desired information. Errors occurred when all dyads, except number 001, attempted to locate the answer in the Health Education Information section. The average ASQ score is 4, indicating a moderate but relatively low level of user satisfaction, highlighting areas for usability improvement.

The SUS scores provided by the 5 dyads range from 57.5 to 87.5, with an average score of 67.5, just below the industry standard threshold of 68. This indicates that users found the platform to be marginally acceptable in terms of usability, indicating areas for improvement. In combination with the performance and ASQ ratings of the 6 tasks, it was observed that the 3 tasks involving operations on the extended app (ie, Record Values, Reminder Settings, and Kidney Health Mission) all achieved a 100% success rate, with shorter completion times, fewer operational errors, and higher satisfaction (mean average ASQ score: 5.64 vs 3.87 for the other 3 tasks). Conversely, tasks with lower performance and ASQ scores (ie, Health Education Information, Kidney Support Teammate, and Inquiry & Consultation) all involved finding information within LINE OA, suggesting that underlying significant usability issues in this area may have contributed to the low overall platform SUS score.

Our study encompassed participants with diverse backgrounds, ranging from health care providers (including nephrologists and nurses) within the institution involved in phase 1 system development, to patients with CKD and SOs engaged in both phase 1 platform trial use and phase 3 usability testing. Health care and electrical engineering experts from external institutions were involved in phase 2 heuristic evaluation. Of these participants, 41.7% (10/24) were male, spanning ages from 28 to 82 years, and educational attainment ranging from elementary school to doctoral degrees. Such diversity maximized the input from all potential stakeholders who could use or benefit from our digital platform. We ensured that various perspectives were considered throughout the development cycle, thereby optimizing platform usability while accommodating user differences.

Notably, the design of including SOs with patients with CKD in our study was pivotal. It not only enriched the diversity of perspectives but also prevented the exclusion of patients who might face challenges participating independently, such as those from older age groups or with lower educational levels, potentially constituting digitally disadvantaged groups. This inclusive approach, exemplified by dyads numbers 004 and 005 (Table 5), served to mitigate selection bias and promote health equity at the digital resource level.

In a 2023 internet survey conducted in Taiwan, it was found that 98.51% of internet users use instant messaging tools, with LINE holding a dominant market share of 91.61% [38]. Our digital platform operates within Taiwan’s most prevalent instant messaging app, significantly improving its accessibility and ubiquity. This integration closely aligns CKD self-management with the most frequent daily use of digital technology. Data extracted from the backend of the LINE OA further revealed consistent user engagement with our digital platform, with more than 90% of interactions being automatic Push or Reply messages (Table 6). This underscores the high automation and low-cost model of our digital platform, demonstrating its potential for scalable application in medical settings.

Figure 5 further illustrates the interactive relationship between CKD dyads, the research team, and health care providers, elucidating how our digital platform can enhance CKD care in medical settings. The green arrow at the bottom represents patients with CKD and their SOs seeking routine care at the hospital. Blue arrows depict CKD dyads using LINE OA, either through encouragement or voluntary interaction, to stay connected with the research team (communication strategy); or using the extended app to log home-based health records, including blood pressure, diet, medication, and physical activity (monitoring strategy). Red arrows signify the fully automated services offered by our digital platform, such as providing health education information through LINE OA Push or Reply messages (education strategy); or accessing physiological trend charts and usage reports via the extended app (feedback strategy). Orange arrows indicate the interventions that the research team can deliver through the digital platform, such as maintaining contact with CKD dyads (communication strategy); or answering CKD dyads’ queries and sending encouraging messages (feedback strategy) via LINE OA. Finally, the research team can further analyze and aggregate home-based self-monitoring records logged by CKD dyads through the extended app (analysis strategy) and provide reports to health care providers. This additional information will furnish health care providers with supplementary insights during CKD dyads’ visits, aiding in treatment recommendations to enhance the quality of CKD care.

This study provides empirical evidence of high user acceptance and satisfaction with our digital platform, as indicated by self-reported satisfaction ratings and intentions to continue usage during phase 1 trial use, as well as by the ASQ scores obtained from phase 3 usability testing. While self-reported ratings could potentially be inflated by demand characteristics [39,40], the robustness of these findings is further supported by users’ consistent execution of the 2 daily self-management tasks. As depicted in Table 7, more than half of the 10 trial users maintained an EAR from 50% to 100% for the 2 daily tasks for more than 6 months. Notably, 5 users had a record of executing the 2 daily tasks consecutively for 30 days or more, demonstrating their ability to sustain regular usage. These findings imply their persistent commitment to using our digital platform for managing CKD, even after they completed the study. Such ongoing engagement serves as compelling evidence of our digital platform’s potential as a highly acceptable digital health solution, empowering CKD dyads in the process of lifestyle modification.

Despite the wide availability of our digital platform on LINE OA and the inclusive dyadic design, this study might still have suffered from selection bias due to digital divides between those with access to our platform and those without [41]. During phase 1 participant recruitment, we encountered instances where some CKD dyads, particularly spouses, reported lacking access to smartphones or the internet. Conversely, some dyads had smartphones with internet access but lacked diverse digital skills or did not have LINE installed on their phones. All these factors could impede the implementation of our study and raise concerns over health inequity. Although the extent of these digital divides was not thoroughly investigated within the scope of this study, their existence warrants careful consideration in our future work to prevent selection bias favoring participants with higher digital proficiency.

For participants facing difficulties in using our platform, personalized assistance will be provided through interactive learning sessions and the user manual, reducing the likelihood of their attrition from the study. Furthermore, future research could investigate the prevalence and characteristics of digitally disadvantaged groups within the CKD population. Assessing the severity and underlying causes of digital divides may help mitigate their impact on the implementation of our DHI. Alternatively, programs empowering lifestyle modification tailored to CKD dyads who are not internet or smartphone users could be developed.

Despite continuous optimization, the SUS scores obtained from phase 3 usability testing indicate that the usability of our digital platform remains marginally acceptable. Particularly, significant usability issues were identified within the information layout of the service menu on LINE OA. During phase 1 trial use, dyads reported difficulties navigating sections including Health Education Information, Kidney Support Teammate, and Inquiry & Consultation, often getting lost. Similarly, task performance and user satisfaction related to these sections were relatively low in phase 3 usability testing. However, tracking individual user interactions with specific sections in LINE OA is challenging due to its backend limitations, as only aggregate user activity data are available. This impedes the establishment of personalized sections, as suggested by the heuristic evaluators in phase 2.

Analysis of phase 3 error records further revealed 2 major sources of confusion (Multimedia Appendix 4). First, users were often unsure whether to seek answers in Health Education Information or Inquiry & Consultation, as both sections were perceived to serve a similar purpose of obtaining CKD-related knowledge. This mismatch between users’ mental models and the platform’s menu structure frequently led them to attempt tasks in the wrong section, causing navigation failures. Second, the design of LINE OA as an instant messaging interface posed inherent challenges: the service menu occupies nearly one-third of the small mobile screen, while new messages push earlier information upward, forcing users to scroll back or reselect menu buttons to revisit prior content. When combined with multilayered menu depth, these constraints increased cognitive load and disorientation, further compounding the likelihood of users getting lost.

To overcome these challenges, several measures have been introduced and others are planned. In response to phase 2 feedback, we incorporated a “return to previous level” option within the Kidney Support Teammate and Inquiry & Consultation sections (Figure 2D), providing a route back when disoriented. Future platform refinements could also consolidate Health Education Information and Inquiry & Consultation into a single section, for instance, by embedding Inquiry & Consultation under Health Education Information to reduce functional overlap and user confusion. Moreover, involving CKD dyads in early stages of prototype development remains essential. Interviews on information needs and common questions could align menu structures more closely with users’ mental models. Finally, harnessing the instant messaging nature of LINE OA, the inclusion of a chatbot could provide more efficient and context-sensitive access to disease-related information through automated dialogue interactions, thereby enhancing overall usability [21].

Despite our efforts to simplify the design of our digital platform, reducing hierarchies and operational paths, along with manual support and relevant skill teachings, some users, as shown in Table 7, have an activity rate below 50% for logging physiological values (2 users) or writing kidney diaries (4 users). We identified 3 potential reasons for these low EARs, indicating the need for more comprehensive interventions as mentioned in the following sections.