Psychometric evaluation of the Diabetes Injection Device Experience Questionnaire (DID-EQ) and Diabetes Injection Device Preference Questionnaire (DID-PQ)

Journal of Patient-Reported Outcomes

Table 2 DID-EQ: Descriptive Statistics and Exploratory Factor Analysis

Item	N	Mean	SD	Range	Floor (%)^a	Ceiling (%)^a	EFA Factor Loadings^b
1. How difficult is it to prepare the injection device and medication for use?	142	3.7	0.6	1.0–4.0	1 (0.7%)	101 (71.1%)	0.5418
2. How difficult is it to fit the injection into your routine?	142	3.6	0.6	2.0–4.0	0 (0.0%)	95 (66.9%)	0.6105
3. How difficult is it to bring the injection device with you when it is necessary to inject away from home?	140	3.3	0.7	2.0–4.0	0 (0.0%)	67 (47.9%)	0.4858
4. How confident are you that the injection device provides the correct dose of medication every time?	142	3.3	0.8	1.0–4.0	2 (1.4%)	70 (49.3%)	0.6548
5. How confident are you that you are using the injection device correctly?	141	3.4	0.7	2.0–4.0	0 (0.0%)	78 (55.3%)	0.6654
6. How satisfied are you with the size of the needle?	142	3.5	0.8	1.0–4.0	4 (2.8%)	90 (63.4%)	0.6612
7. How satisfied are you with the time it takes to prepare and inject each dose of medication?	141	3.6	0.7	1.0–4.0	2 (1.4%)	103 (73.0%)	0.5769
Device Characteristics Subscale	142	83.0	15.8	38.1–100.0	0 (0.0%)	33 (23.2%)	–
8. Overall, I am satisfied with the injection device.	142	3.5	0.6	1.0–4.0	1 (0.7%)	81 (57.0%)	–
9. Overall, it is easy to use the injection device.	142	3.5	0.6	2.0–4.0	0 (0.0%)	84 (59.2%)	–
10. Overall, it is convenient to use the injection device.	142	3.5	0.6	2.0–4.0	0 (0.0%)	80 (56.3%)	–

^a These percentages indicate the percent of patients at the floor and ceiling of the possible range of each item
^b Exploratory factor analysis (EFA) of the seven items included in the Device Characteristics subscale of the final DID-EQ (1-factor solution with oblique rotation)