My Diabetes Care Mobile: A 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 85 or above suggests excellent usability. The SUS has been used in several studies of patient facing health information technology (the article describing its psychometric properties has been cited over 500 times) and has excellent internal consistency reliability (Cronbach's alpha of 0.91).

Self-reported usage of My Diabetes Care to include total number of participants who visited MDC-m during the study period and total number of participants with who used MDC-m for 10 minutes or more during the study period.

Unique study specific items to assess participants' perspectives on the usefulness of particular My Diabetes Care features and functionality.

The Short Diabetes Knowledge Instrument (SDKI) is a valid measure of diabetes knowledge with an emphasis on controlling blood glucose through diet, recognizing symptoms of abnormal blood glucose, and using healthy eating to prevent complications. It also includes items on foot care and the importance of physical activity for preventing cardiovascular complications. The SDKI is a uni-dimensional, 13-item scale with scores ranging from 0 to 13 (number of items answered correctly). SDKI demonstrated good internal consistency reliability (Cronbach's alpha 0.73) in a multi-ethnic sample of older adults suggesting the instrument can be used to measure diabetes knowledge in diverse populations (Quandt et al. Diabetes Educator, 2014).

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.

Unique study specific items to assess participants' knowledge of measures of diabetes health status (i.e., Hemoglobin A1C, blood pressure, low-density lipoprotein, and flu vaccination status). Each multiple choice item has one correct answer and the unit of measure is the number of participants that correctly answered each item.

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 has excellent excellent internal consistency reliability (Cronbach's alpha 0.86) and is associated with measures of depression and hemoglobin A1c.

Unique study specific items to assess participants' attitudes toward social comparisons (2 items) and goal-based comparisons (2 items) regarding their diabetes health status. Each items is scored on a 5-point Likert scale from '1=strongly disagree' to '5=strongly agree'.

Four-item assessment of stage of change based on the Transtheoretical Model (TTM) of behavior change. It includes questions one item each assessing the participants stage of change 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 for the item: (a) Precontemplation, (b) Contemplation, (c) Preparation, (d) Action, and (e) Maintenance.

The Summary of Diabetes Self-Care Activity (SDSCA) is a 10-item multidimensional instrument to assess levels of diabetes self-care across five domains: general diet (2 items), specific diet (2 items), exercise (2 items), foot care (2 items), and blood-glucose testing (2 items). The general diet subscale is used to assess general 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: general diet (2 items), specific diet (2 items), exercise (2 items), foot care (2 items), and blood-glucose testing (2 items). The general diet subscale is used to assess general 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: general diet (2 items), specific diet (2 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. An example item includes "On how many of the last SEVEN DAYS did you participate in at least 30 minutes of physical activity?" 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: general diet (2 items), specific diet (2 items), exercise (2 items), foot care (2 items), and blood-glucose testing (2 items). The blood-glucose testing subscale is used to assess self-monitoring of blood glucose adherence. The instrument is based on the self-reported days completing recommended activities during the past 7 days. An example item includes "On how many of the last SEVEN DAYS did you test your blood sugar?" The blood-glucose testing subscale 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 Adherence to Refills and Medications Scale is a reliable and valid measure of medication adherence. The 12-item ARMS has good internal consistency reliability (α=0.81). Responses range from 1="none of the time" to 4="all of the time," and are summed to produce an overall adherence score ranging from 12-48, with higher scores representing more problems with medication adherence.