My Diabetes Care: A Scalability and Usability Study

The System Usability Scale (SUS) is a valid measure of usability and assesses users' perceptions of ease of use, likability of the interface, and overall satisfaction using a 5- point Likert scale (strongly disagree to strongly agree). The ten items are scored on a five-point Likert scale. The item scores are summed and then converted to a score ranging from 0 (worst) to 100 (best). Based on prior research, a score above 68 would be above average and a score of 71 or above suggests 'good' usability.

System usage will be assessed by user analytics data capturing participant use to MDC during the study period. MDC use is defined as one or more visits to the MDC site during the study period.

User experience will be assessed by study-specific survey items administered to all study participants at the end of the study period (T1). Survey items will assess agreement on a 5-point Likert scale from Strongly Agree to Strongly Disagree. Participants will be asked whether they would continue to use My Diabetes Care (MDC) going forward were it to remain available and whether they would recommend MDC to other patients with diabetes.

The Revised Brief Diabetes Knowledge Test (DKT2) is a valid measure of diabetes knowledge. The 14-item questionnaire was designed to assess a patient's understanding of diabetes management. The DKT2 is a uni-dimensional, 14-item scale with scores ranging from 0 to 14 (number of items answered correctly). Higher scores indicate greater knowledge.

The Summary of Diabetes Self-Care Activity (SDSCA) is a 10-item multidimensional instrument to assess levels of diabetes self-care across five domains: diet (4 items), exercise (2 items), foot care (2 items), and blood-glucose testing (2 items). The general diet subscale is used to assess diet adherence. The instrument is based on the self-reported days completing recommended activities during the past 7 days. An example item includes "How many of the last SEVEN DAYS have you followed a healthful eating plan?" The general diet subscale score is the mean number of days for the 2 items in the subscale. The score range is from 0 days (worst) to 7 days (best).

The Summary of Diabetes Self-Care Activity (SDSCA) is a 10-item multidimensional instrument to assess levels of diabetes self-care across five domains: diet (4 items), exercise (2 items), foot care (2 items), and blood-glucose testing (2 items). The exercise subscale is used to assess exercise adherence. The instrument is based on the self-reported days completing recommended activities during the past 7 days. The exercise subscale score is the mean number of days for the 2 items in the subscale. The score range is from 0 days (worst) to 7 days (best).

The Summary of Diabetes Self-Care Activity (SDSCA) is a 10-item multidimensional instrument to assess levels of diabetes self-care across five domains: diet (4 items), exercise (2 items), foot care (2 items), and blood-glucose testing (2 items). The blood-glucose testing subscale is used to assess glucose self-monitoring adherence. The instrument is based on the self-reported days completing recommended activities during the past 7 days. The blood-glucose testing subscale score is the mean number of days for the 2 items in the subscale. The score range is from 0 days (worst) to 7 days (best).

The Perceived Diabetes Self-Management Scale (PDSMS) is a valid measure of diabetes self-efficacy (i.e., how confident they feel about their ability to carry out multiple self management tasks). The uni-dimensional, 8-item scale is scored on a five-point Likert scale. The total PDSMS score can range from 8 to 40, with higher scores indicating more confidence in self-managing one's diabetes.

The Adherence to Refills and Medications Scale is a reliable and valid measure of medication adherence. The 12-item scale has item responses range that from 1="none of the time" to 4="all of the time." Responses are summed to produce an overall adherence score ranging from 12-48, with higher scores representing more problems with medication adherence.

The Problem Areas in Diabetes Scale (PAID-5) is a valid measure of diabetes distress. The five-item, uni-dimensional scale has scores that range from 0 to 20, with higher scores suggesting greater diabetes-related emotional distress. The PAID-5 is associated with measures of depression and hemoglobin A1c.

Unique study specific items to assess participants' knowledge of measures of diabetes health status (i.e., hemoglobin A1C, blood pressure, low-density lipoprotein, urine microalbumin, and body mass index). Each item has 1 correct answer and several incorrect answers.

Four-item assess the participants' stage of change based on the Transtheoretical Model (TTM) of behavior change including one item each for: (1) physical activity, (2) medication management, (3) glucose self-monitoring, and (4) diet. There are five response options per item that categorize the participants' current TTM stage of change across a continuum: (a) Precontemplation [worst], (b) Contemplation, (c) Preparation, (d) Action, and (e) Maintenance [best]. For each item, precontemplation is represented by the response "No, and I do not intend to in the next 6 months"; contemplation is represented by the response "No, but I am thinking about starting in the next 6 months"; Preparation is represented by the response "No, but I am planning to start in the next 30 days"; action is represented by the response "Yes, I have been for less than 6 months"; and maintenance is represented by the response "Yes, I have been for 6 months or more."