Development and Psychometric validation of the Diabetes Therapy-Related QOL (DTR-QOL) Questionnaire

Figures & data

Table 1.  Backgrounds of the analysis set (n = 284).

Characteristics
Age (n, Mean ± SD)	280	64.0 ± 11.6
Sex (n, %)
Male	170	59.9
Female	114	40.1
Diabetes type (n, %)
Type 1	22	7.8
Type 2	260	92.2
Treatment (n, %)
Diet alone	35	12.3
Oral antidiabetic drug(s) alone	117	41.2
Insulin alone	107	37.7
Insulin + Oral antidiabetic drug(s)	25	8.8
Concomitant disease (n, %)
Nephropathy
Yes	84	30.0
No	196	70.0
Retinopathy
Yes	84	30.8
No	189	69.2
Neuropathy
Yes	116	41.1
No	166	58.9
HbA1c (% [NGSP value]) (n, Mean ± SD)	283	7.2 ± 0.9

Table 2.  Construct validity (the evaluation of domain structure): factor loading.

Item no.	Factor 1	Factor 2	Factor 3	Factor 4
1	0.62	0.11	−0.03	−0.02
2	0.67	0.05	0.03	0.06
3	0.71	−0.06	−0.03	0.11
4	0.72	−0.10	0.14	0.05
5	0.71	0.12	−0.03	−0.19
6	0.75	−0.02	0.03	−0.01
7	0.64	0.14	−0.03	−0.03
8	0.43	0.40	−0.15	0.04
9	0.39	0.44	−0.17	0.07
10	0.65	0.05	0.14	0.05
11	0.72	0.08	−0.03	0.06
12	0.49	−0.09	0.20	0.01
13	0.42	−0.02	0.14	−0.07
14	0.19	0.46	0.09	−0.11
15	0.12	0.07	0.66	0.07
16	0.02	0.05	0.90	0.01
17	0.02	0.01	0.93	−0.03
18	0.02	0.04	0.89	0.00
19	0.03	0.66	0.22	−0.15
20	−0.13	0.90	−0.07	−0.02
21	−0.03	0.65	0.18	0.10
22	0.03	0.62	0.10	0.14
23	0.14	0.61	0.09	0.10
24	0.06	0.63	0.04	0.10
25	0.16	0.52	−0.03	0.13
26	−0.12	0.26	−0.09	0.61
27	−0.10	0.20	0.01	0.69
28	0.06	−0.09	0.05	0.73
29	0.10	−0.07	0.04	0.72
Factor contribution rate	0.62	0.14	0.11	0.05

Notes: Principal factor method (promax rotation) was used.

indicates factor pattern ≥0.4

indicates attributed domain

Table 3.  DTR-QOL domain structure.

Factor 1: Burden on social activities and daily activities
1	My current diabetes treatment interferes with my work and activities.
2	My current diabetes treatment limits the scope of my activities.
3	It is difficult to find places on time for my current diabetes treatment.
4	My current diabetes treatment interferes with group activities and personal friendships.
5	It is a burden getting up at a certain time every morning for my current diabetes treatment.
6	With my current diabetes treatment, the restricted meal times are a burden.
7	When I eat out, it is difficult to manage my current diabetes treatment.
8	I feel like my current diabetes treatment takes away the enjoyment of eating.
9	With my current diabetes treatment, it is hard to curb my appetite.
10	The time and effort to manage my current diabetes treatment are a burden.
11	I am constantly concerned about time to manage my current diabetes treatment.
12	Pain due to my current diabetes treatment is uncomfortable.
13	Gastrointestinal symptoms (nausea, passing gas, diarrhea, abdominal pain) due to my current diabetes treatment are uncomfortable.
Factor 2: Anxiety and dissatisfaction with treatment
14	I am bothered by weight gain with my current diabetes treatment.
19	I have uncomfortable symptoms due to hyperglycemia (high blood glucose).
20	I am worried about high blood glucose.
21	I am dissatisfied that my blood glucose is unstable (high and low).
22	I am worried that complications might get worse with my current diabetes treatment.
23	I get anxious thinking about living while on my current diabetes treatment.
24	I find it unbearable to think that even if I continue my current diabetes treatment, my diabetes may not be cured.
25	I am concerned that if I continue my current diabetes treatment, the efficacy (effectiveness) may diminish.
Factor 3: Hypoglycemia
15	I worry about low blood glucose due to my current diabetes treatment.
16	I am scared because of low blood glucose.
17	I am sometimes bothered by low blood glucose.
18	Symptoms due to low blood glucose are uncomfortable.
Factor 4: Satisfaction with treatment
26	Overall, I am satisfied with my current blood sugar control (glycemic control).
27	With my current diabetes treatment, I am confident that I can maintain good blood glucose control.
28	I am hopeful about the future with my current diabetes treatment.
29	With regards to diabetes treatment, I am satisfied with current treatment methods.

Table 4.  Domain scores and Cronbach α coefficient.

	No. of items	Mean ± SD	Median [Minimum-Maximum]	Cronbach α coefficient
Factor 1: Burden on social activities and daily activities	13	81.4 ± 17.7	85.9 [6.4–100.0]	0.91
Factor 2: Anxiety and dissatisfaction with treatment	8	69.3 ± 23.7	68.8 [6.3–100.0]	0.89
Factor 3: Hypoglycemia	4	79.1 ± 27.2	91.7 [0.0–100.0]	0.93
Factor 4: Satisfaction with treatment	4	66.5 ± 21.5	62.5 [0.00–66.5]	0.81
Total	29	75.7 ± 17.3	77.6 [21.8–100.0]	0.94

Score range: 0–100. The higher score indicates higher QOL.

Table 5.  Concurrent validity: Correlation coefficients between DTR-QOL and the external standards (n = 284).

	DTR-QOL	DTSQ	SF-8 (PCS)*	SF-8 (MCS)†
DTR-QOL	–	0.35	0.34	0.44
DTSQ	0.35	–	0.18	0.19
SF-8 (PCS)*	0.34	0.18	–	0.07
SF-8 (MCS)^†	0.44	0.19	0.07	–

Coefficients are Pearson’s product-moment correlation coefficient, all P values <0.05

*PCS is physical component summary

^†MCS is mental component summary

Table 6.  Discriminant validity: relationship between the factors that may affect the DTR-QOL scores and the actual total scores.

Factors	n	Mean ± SD	P value*
Sex
Male	169	76.6 ± 17.1	0.3077
Female	114	74.4 ± 17.6
Age in years
<65	126	72.3 ± 16.5	0.0035
≥65	153	78.4 ± 17.5
Diabetes type
Type 1	22	60.9 ± 17.0	0.0001
Type 2	259	77.0 ± 16.8
HbA1c
6.9≥	105	80.6 ± 16.6	<0.0001
7.0–8.3	149	74.1 ± 17.0
8.4≤	28	65.7 ± 16.2
Treatment
Diet alone	34	82.3 ± 14.6	<0.0001
Oral antidiabetic drug(s) alone	117	80.7 ± 15.3
Insulin + Oral antidiabetic drug(s)	25	72.6 ± 15.9
Insulin alone	107	68.9 ± 18.1
Glycemic control in the past 1 month (patient assessment)
Very good	30	83.4 ± 16.5	<0.0001
Good	144	79.6 ± 16.9
Neither good nor poor	80	70.1 ± 15.7
Poor	24	65.7 ± 14.5
Very poor	4	54.9 ± 10.6
Hypoglycemia in the past 1 month
Yes	64	65.8 ± 18.3	<0.0001
No	216	78.7 ± 15.9
Nocturnal hypoglycemia in the past 1 month
Yes	17	61.5 ± 19.0	0.0004
No	265	76.7 ± 16.8
Concern about weight gain in the past year
Not concerned at all	116	81.4 ± 15.7	<0.0001
Not very concerned	75	75.0 ± 16.9
Maybe a bit concerned	32	72.3 ± 14.5
Somewhat concerned	49	68.0 ± 17.7
Very concerned	9	62.7 ± 22.7
Health status (patient assessment)
Good	85	84.9 ± 14.5	<0.0001
Somewhat good	107	76.2 ± 17.0
Neither good nor poor	57	66.6 ± 15.1
Somewhat poor	32	67.8 ± 14.6
Poor	1	27.6
Degree of communication on treatment with physician
Good communication	155	78.7 ± 16.8	0.0098
Some communication	108	73.2 ± 17.5
Cannot say one way or the other	13	68.9 ± 14.9
Not much communication	5	63.7 ± 18.9
No communication	1	52.9

*For 2 categories, the unpaired t-test was used, and for ≥3 categories, analysis of variance was used.