Validating a Self-Reported Medication Nonadherence Measure in the Context of Multiple Chronic Diseases and Routes of Medication Administration Among Patients with Type 2 Diabetes

Figures & data

Figure 1 Final two-part measure of extent of, and reasons for, nonadherence to injectable diabetes medications.

Notes: The measure is copyrighted by Duke University. For permission to use it, please contact Duke University’s Office of Translation and Commercialization.

Table 1 Participant Characteristics

	Study 1 (n=14)	Study 2 (n=12)
Age in years, M (SD)	56.2 (9.3)	61.5 (10.3)
Assigned male at birth, n (%)	14 (35.7)	5 (41.7)
Race
White	14 (100)	9 (75)
Black	0 (0)	2 (16.7)
Hispanic ethnicity	0 (0)	2 (16.7)
Marital status
Single, never married	4 (28.6)	1 (8.3)
Married/Living together	9 (64.2)	8 (66.7)
Divorced/Separated/Widowed	1 (15.5)	3 (25)
Education level
High school graduate/equivalent or less	1 (7.1)	1 (8.3)
Trade/technical/vocational or some college	6 (42.9)	4 (33.3)
Bachelor’s degree	4 (28.6)	7 (58.3)
Post graduate work or graduate degree	3 (21.4)	0 (0)
Employment status*
Working full-time or part-time	8 (57.1)	7 (58.3)
Retired	4 (28.6)	6 (50)
Disabled	2 (14.3)	2 (16.7)
Income level
$29,999 or less	2 (14.3)	1 (8.3)
$30,000–49,999	1 (7.1)	3 (25)
$50,000–59,999	2 (14.3)	1 (8.3)
$60,000–79,999	1 (7.1)	3 (25)
$80,000 or more	6 (42.9)	3 (25)
Insurance^a
Health insurance through employer	9 (64.3)	4 (33.3)
Health insurance directly through an insurance provider	2 (14.3)	1 (8.3)
Medicare	5 (35.7)	6 (50)
Medicaid	1 (7.1)	1 (8.3)
Other	1 (7.1)	2 (16.7)
Health Literacy, M (range)^b	35.1 (33–36)	33.6 (25–36)
Diabetes Medication, n (%)
Injectable medication	13 (92.9)	10 (83.3)
Injectable fixed-schedule insulin	9 (64.2)	8 (66.7)
Injectable GLP-1 (taken weekly)	11 (78.6)	6 (50.0)
Oral medication	11 (78.6)	7 (58.3)

Notes: ^aEmployment status and insurance categories are not mutually exclusive. ^bHealth literacy was measured by the Short-Test of Functional Health Literacy in Adults (S-TOFHLA). Missing data, Study 1: Participants declined to provide data for age (n=2), sex assigned at birth (n=1), gender (n=1), income (n=1), and health literacy (n=1). Gender differed from sex assigned at birth for one participant. Missing data, Study 2: Participants declined to provide data for age (n=1), race and ethnicity (n=1), and income (n=1). Two participants did not complete the S-TOHFLA due to technical difficulties.

Table 2 Results of Cognitive Interviews for Study 1 (Oral and Injectable Diabetes Medications) and Study 2 (Diabetes, Blood Pressure, and Cholesterol Medications)

Study	Round	Item or Issue Evaluated	Results
Instructions
1	1	Instructions for combined version: “When responding, please think about both your diabetes pills and injectable medicines.”	Participants thought they could report more accurately if asked to complete separate oral and injectable versions, especially if prescribed weekly and daily medications.
2	1–2	Instructions for combined version: “When responding, please think about all of your blood pressure, cholesterol, and diabetes medicines.	Participants thought they could report more accurately if asked to complete separate disease-specific versions; participants were not bothered by the repetition or time to complete multiple questionnaires and preferred the increased accuracy.
1,2	1	Instructions for completing reasons for nonadherence items: “Situations come up that make it difficult for people to take their medication as prescribed by their doctors. Below is a list of those situations. We want to know how much these situations contributed to you missing a dose of your (insert disease, route) medicine. Only one of these situations may apply to you, or many may apply to you.”	Participants did not know how to respond when they took doses “late” as this could be considered as missing a dose. This led us to add an instruction (see next item).
1,2	2	Added instruction: “If you were late but still took the medicine, it does not count as a missed dose.”	“Late” was interpreted as late in the day. This led to further revisions to the instructions (see next item).
1,2	3	Revised instruction: “If you took it later than prescribed, it does not count as a missed dose.”	“Than prescribed” did not always apply because dosing instructions were not always specific regarding time, and medication taking was often tied to an activity (eg, take with a meal).
1,2	4	Revised instruction: “If you took the medicine later than usual but still took it, it does not count as a missed dose.”	Interpreted as intended
1,2	1–3	7-day recall period for all injectable medications	Did not fit weekly medications for which the answer should be yes/no; participants felt they could remember longer time periods for weekly medications.
1,2	4	One-month recall period for weekly injectable medications	Participants felt they could recall 1 month accurately for weekly injectable medications; response scale for extent of nonadherence fit this longer time period.
1,2	3	Based on participant desire to respond about more than 7 days, we added instruction for weekly medications: “We recognize that the past 7 days may not represent what you do over longer time periods. However, we are only interested in the past 7 days.”	Participants responded about the past 7 days.
	Extent of Nonadherence items
1,2	1–4	I missed my medicine	Perceived as addressing unintentional nonadherence; no changes made
1,2	1–4	I skipped a dose of my medicine	Perceived as addressing intentional nonadherence; no changes made
1,2	1–4	I did not take a dose of my medicine	Perceived as addressing unintentional or intentional nonadherence; no changes made
	Reasons for Nonadherence items
1,2	1	New item: I could not see well enough to prepare the injection^a	Interpreted as intended, relevant
1,2	1	New item: I had trouble with my hands in preparing the medicine^a	Interpreted as intended, relevant
1,2	1	New item: I do not like needles^a	Interpreted as intended, relevant
1,2	1	New item: I could not find a place on my body to inject the needle^a	Interpreted as intended, relevant
1,2	1	New item: The injection causes pain^a	Interpreted as intended, relevant
1,2	1	New item: I was not able to check my blood sugar^a	Interpreted as intended, relevant
1,2	1	New item: I did not have a place to refrigerate my medicine^a	Interpreted as intended, relevant
1,2	1	New item: I did not have the supplies needed to take the medicine^a	Interpreted as intended, relevant
1,2	2	New item: I did not have time to prepare my medicine^a	Interpreted as intended, relevant
1,2	1	Existing item: I could not afford the medicine^b	Perceived as judgmental
1,2	2	Revised item: The medicine was too expensive^b	Acceptable, interpreted as intended, relevant

Notes: ^aAdded to the diabetes-specific version. ^bAdded to all versions.