Patients’ and physicians’ preferences for type 2 diabetes mellitus treatments in Spain and Portugal: a discrete choice experiment

Figures & data

Figure 1 Example of choice question convenience attributes.

Figure 2 Example of choice question clinical attributes.

Abbreviation: HbA_1c, glycated hemoglobin.

Table 1 Attributes and levels for the choice questions

Attributes	Levels
Mode of administration	Injections twice a day in relation to meals
	Injection once a day in relation to meals
	Injection once a day irrespective of meals
	Oral antidiabetics (OAD) up to three times a day with meals
Blood glucose monitoring	Three times a day
	Once a day
	Three times per week
	No need for testing
Number of hypoglycemic events	None
	Once a week
	Once a month
	Once a year
HbA1c	<6%
	6%–7%
	7%–8%
	>8%
Weight change in 6 months	Gain 3 kg
	Remains the same weight
	Loses 3 kg
	Loses 6 kg
Nausea	Mild nausea for up to 3 months
	None
Cardiovascular risk	Decreases
	Remains the same
Additional payment per month	€100
	€50
	€20
	€0

Abbreviation: HbA_1c, glycated hemoglobin.

Table 2 Patients’ and physicians’ sociodemographic and clinical characteristics

Patients’ sociodemographic characteristic	Spain		Portugal		Total
	Mean	SD	Mean	SD	Mean	SD
Age (years)	62.29	10.24	62.93	9.20	62.39	10.27
Time since diagnosis (years)	14.32	8.39	12.15	7.03	13.98	8.22
Weight (kg)	86.25	17.69	85.69	15.41	86.17	17.33
Height (cm)	162.56	10.27	165.25	8.89	162.99	10.36
BMI (kg/m^2)	32.70	7.01	31.45	5.69	32.50	6.82
	n	%	n	%	n	%
Country	278	84	52	16	330	100
Sex
Female	143	51.4	21	40.4	164	49.7
Male	133	47.8	31	59.6	164	49.7
Level of education
Primary school	146	52.50	32	61.50	178	53.90
Secondary school	74	26.60	12	23.10	86	26.10
University	41	14.70	5	9.60	46	13.90
Postgraduate	3	1.10	2	3.80	5	1.50
Other studies	12	4.30	1	1.90	13	3.90
Annual income
<€12,000	129	46.40	31	59.60	160	48.50
€12,000–€20,000	74	26.60	13	25.00	87	26.40
€20,000–€30,000	48	17.30	3	5.80	51	15.50
€30,000–€50,000	11	4.00	4	7.70	15	4.50
>€50,000	2	0.70	1	1.90	3	0.90
Weight change since diagnosis
Unchanged	46	16.50	15	28.80	61	18.50
Has lost weight	75	27.00	15	28.80	90	27.30
Has gained 0–2 kg	24	8.60	6	11.50	30	9.10
Has gained 2–5 kg	39	14.00	6	11.50	45	13.60
Has gained 5–10 kg	38	13.70	5	9.60	43	13.00
Has gained >10 kg	54	19.40	5	9.60	59	17.90
T2DM complications
None	123	44.24	32	61.54	155	46.97
Eye disease	69	24.82	6	11.54	75	22.73
Kidney problems	65	23.38	3	5.77	68	20.61
Heart disease	79	28.42	6	11.54	85	25.76
Male impotence	19	6.83	3	5.77	22	6.67
Nervous disease	17	6.12	1	1.92	18	5.45
Others	21	7.55	4	7.69	25	7.58
Frequency of hypoglycemia
One hypoglycemia per week	27	9.7	1	1.9	28	8.5
One hypoglycemia per month	62	22.3	6	11.5	68	20.6
One hypoglycemia per year	90	32.4	8	15.4	98	29.7
Never had an hypoglycemia	99	35.6	37	71.2	136	41.2
Last HbA1c level measured (%)
>9	46	16.50	3	5.80	49	14.80
8–9	42	15.10	6	11.50	48	14.50
7–8	104	37.40	25	48.10	129	39.10
<6	42	15.10	9	17.30	51	15.50
Frequency of blood glucose monitoring
Three times a day	46	16.50	3	5.80	49	14.80
Once a day	42	15.10	6	11.50	48	14.50
Three times a week	104	37.40	25	48.10	129	39.10
Once a month	42	15.10	9	17.30	51	15.50
None	35	12.60	9	17.30	44	13.30
Nausea due to T2DM treatment
Yes	45	16.20	8	15.40	53	16.1
No	233	83.80	44	84.60	277	83.9
Mode of treatment administration
Injections +3/day in relation to meals	90	32.37	3	5.77	93	28.18
Injections 2/day with meals	30	10.79	4	7.69	34	10.30
Injections 1/day, not related to meals	86	30.94	5	9.62	91	27.58
OAD 1–2/day, with meals	137	49.28	41	78.85	178	53.94
Physicians’ sociodemographic characteristic	Mean	SD	Mean	SD	Mean	SD
Age (years)	42.48	10.65	39.33	9.63	41.87	10.51
Time since the beginning of practice (years)	15.43	11.35	13.35	9.69	15.02	11.06
	n	%	n	%	n	%
Country	178	80.5	43	19.5	221	100.00
Sex
Female	105	59.00	33	76.70	138	62.40
Male	73	41.00	10	23.30	83	37.60
Specialty
Primary care	104	58	43	100.00	147	66.50
Endocrinologist	74	41.60	0	0	74	33.50

Abbreviations: BMI, body mass index; HbA_1c, glycated hemoglobin; OAD, oral antidiabetics; T2DM, type 2 diabetes mellitus; SD, standard deviation.

Table 3 Patients’ and physicians’ preferences for the treatment attributes

Attribute	Patients (n=330)				Physicians (n=221)				Comparison P-value
	Estimated coefficient (β)	95% CI		P-value	Estimated coefficient (β)	95% CI		P-value
Administration: injection twice a day in relation to meals (reference)
Injection 1/day in relation to meals	1.0668	0.6722	1.4614	<0.001	1.8143	1.2933	2.3353	<0.001	0.0248
Injection 1/day irrespective of meals	1.7417	1.2378	2.2457	<0.001	2.5146	1.7628	3.2665	<0.001	0.0939
OAD up to 3/day with meals	2.3210	1.9128	2.7292	<0.001	2.4662	1.9705	2.9620	<0.001	0.6707
Blood glucose monitoring (per month)	−0.0141	−0.0184	−0.0098	<0.001	−0.0346	−0.0411	−0.0282	<0.001	0.0000
Additional payment per month	−0.0416	−0.0478	−0.0354	<0.001	−0.0263	−0.0328	−0.0197	<0.001	0.0009
Hypoglycemic event: 1/week (reference)
Hypoglycemic events: 1/year	−0.0622	−0.6633	0.5390	<0.001	2.6547	1.9268	3.3826	<0.001	0.1077
Hypoglycemic events: 1/month	0.9227	0.4015	1.4439	0.8394	0.9641	−0.1329	2.0610	0.0850	0.0002
Hypoglycemic events: none	0.9976	0.5935	1.4017	<0.001	1.8995	1.3409	2.4580	<0.001	0.0103
HbA1c (%)	−0.4695	−0.5958	−0.3431	<0.001	−0.8329	−1.0123	−0.6534	<0.001	0.0012
Weight: gain 3 kg (reference)
Weight: remains the same	1.3176	1.0028	1.6324	<0.001	1.1037	0.7358	1.4716	<0.001	0.3935
Weight: lose 3 kg	2.1698	1.2180	3.1216	<0.001	0.9808	−0.5174	2.4789	0.1995	0.1904
Weight: lose 6 kg	1.8155	1.3278	2.3032	<0.001	1.5389	1.0485	2.0293	<0.001	0.4416
Mild nausea for up to 3 months (reference)
Nausea: none	0.8265	0.4049	1.2481	<0.001	0.9478	0.3506	1.5451	<0.001	0.7578
CVR: remains the same (reference)
CVR: decreases	0.8318	0.3715	1.2920	<0.001	1.0206	0.3865	1.6546	<0.001	0.6496
Additional payment per month	−0.0193	−0.0235	−0.0152	<0.001	−0.0066	−0.0122	−0.0010	<0.001	0.0004

Note: Bold values indicate significance value P<0.05.

Abbreviations: CI, confidence interval; CVR, cardiovascular risk; HbA_1c, glycated hemoglobin; OAD, oral antidiabetics.

Table 4 Patients’ and physicians’ willingness to pay for diabetes treatment attributes

Attribute	Unit change	Patients			Physicians
		Monthly WTP (€)	95% CI		Monthly WTP (€)	95% CI
			Inferior (€)	Superior (€)		Inferior (€)	Superior (€)
Hypoglycemic events	Avoid one hypoglycemic event/month	54.80*	23.29	82.26	287.18	160.31	1,387.21
	Avoid one hypoglycemic event/week	51.59*	37.79	64.26	141.42	13.95	613.62
	Avoid one hypoglycemic event/year	3.87	0.34	24.81	114.18	35.29	409.49
Weight	Avoid gaining 3 kg/6 months	68.14	54.55	85.08	166.87	88.63	843.09
	Reduce 6 kg/6 months	25.75**	8.18	48.00	65.80	9.34	411.52
	Reduce 3 kg/6 months	44.07**	7.07	84.80	18.59	2.80	835.62
CVR	Decrease CVR	43.01	20.46	62.83	154.30	98.13	434.19
Nausea	Avoid nauseas	42.74	23.89	61.77	143.30	73.39	543.62
HbA1c	Avoid increasing HbA1c by 1%	24.28	18.41	30.31	125.92	73.30	622.75
Mode of administration	OAD instead of injections in relation to meals	30.16	25.33	34.86	69.07	44.99	100.39
	One injection less per day	25.65	17.09	35.91	26.66	11.79	45.89
	Administration irrespective of meals instead of in relation to meals	16.23	9.84	22.59	24.82	16.07	33.55
	OAD instead of injections irrespective of meals	13.93	7.63	20.55	1.84	0.27	22.25
Blood glucose monitoring	One blood glucose monitoring test less/day	10.19	7.18	13.91	39.55	27.61	56.18
	One blood glucose monitoring test less/month	0.34	0.24	0.46	1.32	0.92	1.87

Note:

* Difference not statistically significant (P=0.8394).

** Difference not statistically significant (P=0.3826).

Abbreviations: CI, confidence interval; CVR, cardiovascular risk; HbA_1c, glycated hemoglobin; OAD, oral antidiabetics; WTP, willingness to pay.

Table 5 Physicians’ and patients’ preferences for the convenience attributes

Patients’ preferred treatment	Mode of administration	Blood glucose monitoring	Additional payment/month (€)	Physicians’ preferred treatment
1	Injection 1/day irrespective of meals	Three times per week	0	1
2	OAD up to 3/day with meals	No need for testing	20	2
3	Injection 1/day in relation to meal	No need for testing	0	3
4	OAD up to 3/day with meals	Three times a day	0	9
5	Injection 1/day irrespective of meals	Once a day	20	5
6	OAD up to 3/day with meals	Once a day	50	6
7	Injection 1/day irrespective of meals	No need for testing	50	4
8	Injection 2/day in relation to meals	Once a day	0	11
9	Injection 2/day in relation to meals	Three times per week	20	10
10	Injection 1/day in relation to meals	Three times a day	20	12
11	Injection 1/day in relation to meals	Three times per week	50	7
12	OAD up to 3/day with meals	Three times per week	100	8
13	Injection 2/day in relation to meals	Three times a day	50	16
14	Injection 1/day in relation to meals	Once a day	100	13
15	Injection 1/day irrespective of meals	Three times a day	100	15
16	Injection 2/day in relation to meals	No need for testing	100	14

Abbreviation: OAD, oral antidiabetics.

Table 6 Physicians’ and patients’ preferences for the clinical attributes

Patients’ preferred treatment	No of hypoglycemic events	HbA1c	Weight change/6 months	Nauseas/3 months	CVR	Additional payment per month (€)	Physicians’ preferred treatment
1	1/year	6%–7%	Lose 6 kg	None	Decreases	0	1
2	1/week	<6%	Lose 3 kg	None	Decreases	20	4
3	None	7%–8%	Lose 6 kg	None	The same	20	5
4	1/month	<6%	Lose 6 kg	Mild nausea	Decreases	50	3
5	None	>8%	The same	None	Decreases	50	7
6	None	6%–7%	Lose 3 kg	Mild nausea	Decreases	100	6
7	1/month	>8%	Lose 3 kg	None	The same	0	14
8	1/week	7%–8%	The same	Mild nausea	Decreases	0	13
9	1/year	<6%	The same	None	The same	100	2
10	None	<6%	Gain 3 kg	Mild nausea	The same	0	8
11	1/month	6%–7%	The same	Mild nausea	The same	20	10
12	1/year	7%–8%	Lose 3 kg	Mild nausea	The same	50	9
13	1/year	>8%	Gain 3 kg	Mild nausea	Decreases	20	11
14	1/week	6%–7%	Gain 3 kg	None	The same	50	15
15	1/month	7%–8%	Gain 3 kg	None	Decreases	100	12
16	1/week	>8%	Lose 6 kg	Mild nausea	The same	100	16

Abbreviations: CVR, cardiovascular risk; HbA_1c, glycated hemoglobin; No, number.

Figure 3 Comparison of physicians’ and patients’ monthly WTP for diabetes treatment attributes.

Abbreviations: HbA_1c, glycated hemoglobin; WTP, willingness to pay.

Table S1 Patients’ and physicians’ conditioning factors P-values results obtained by the multinomial model

	Convenience attributes (P-value)	Clinical attributes (P-value)
Patients’ characteristics
Sex	0.1706	0.2626
Being >65 years	0.2726	0.9263
Having incomes above €12,000 a year	0.1898	0.6045
Blood glucose control 1/day	0.8984	0.9375
Blood glucose control 3/day	0.4034	0.2662
Blood glucose control 1/month	0.1763	0.8459
No need for glucose control	0.5483	0.1529
Hypoglycemia 1/month	0.3977	0.6653
Hypoglycemia 1/month	0.8749	0.5689
Never had hypoglycemia	0.3856	0.8026
HbA1c 8%–9%	0.5366	0.8342
HbA1c 7%–8%	0.9104	0.7592
HbA1c <6%	0.4873	0.7888
HbA1c unknown	0.5150	0.8570
Obesity	0.5173	0.1160
More than 10 years since the diagnosis	0.0281	0.7682
Receiving injectable treatment	0.0394	0.7395
Physicians’ characteristics
Sex	0.5614	0.0847
Medical specialty	0.3180	0.3051
Time since beginning of practice longer than 10 years	0.0717	0.7243
Country	0.4044	0.1023

Note: Bold values indicate significance value P<0.05.

Abbreviation: HbA_1c, glycated hemoglobin.