Estimating the willingness to pay for a quality-adjusted life year in Thailand: does the context of health gain matter?

Figures & data

Table 1 Characteristics of the respondents based on health scenario

	Blindness scenario (N = 399)	Paralysis scenario (N = 399)	Allergen scenario (N = 393)	All respondents (N = 1191)
Age (year), $\overline{X}$(SD)	39.8 (13.9)	40.0 (13.9)	40.6 (14.5)	40.1 (14.1)
Gender, N (%)
Male^a	175 (43.9)	148 (37.1)	188 (47.8)	511(43)
Marital status, N (%)
Married	269 (67.4)	280 (70.2)	269 (68.4)	818 (68.7)
Single	97 (24.3)	87 (21.8)	91 (23.2)	275 (23.1)
Divorced	33 (8.3)	32 (8.0)	33 (8.4)	98 (8.2)
Education, N (%)
Less than primary school	0 (0)	4 (1.0)	0 (0)	4 (0.2)
Primary school	193 (48.4)	198 (49.6)	198 (50.4)	589 (49.4)
Secondary school	171 (42.9)	163 (40.9)	176 (44.8)	510 (42.8)
Bachelor degree or higher	35 (8.7)	34 (8.5)	19 (4.8)	88 (7.4)
Monthly household income (baht), $\overline{X}$(SD)	15,386 (14,893)	16,168 (19,305)	15,124 (14,482)	15,556 (16,348)
Health insurance scheme, N (%)
Civil servant benefit scheme	34 (8.5)	32 (8.0)	34 (8.7)	100 (8.4)
Universal coverage scheme	316 (79.2)	308 (77.2)	304 (77.6)	928 (77.9)
Social security scheme	30 (7.3)	35 (8.8)	31 (7.9)	96 (8.1)
Out of pocket	12 (3.0)	16 (4.0)	15 (3.8)	43 (1.6)
Current utility, $\overline{X}$(SD)
Measured by TTO	0.91 (0.15)	0.91 (0.16)	0.90 (0.18)	0.91 (0.15)
Measured by VAS	0.76 (0.14)	0.76 (0.15)	0.75 (0.15)	0.76 (0.15)

Note:

a P < 0.05 across health scenarios.

Abbreviations: SD, standard deviation; TTO, time trade off; VAS, visual analog scale.

Table 2 Number of discounted QALYs gained for each health scenario

Health scenario	Number of discounted QALYs gained, $\overline{X}$(SD)
	TTO		VAS
	Severity I^Table Footnotea,Table Footnotec	Severity II^Table Footnoteb,Table Footnotec	Severity I^Table Footnotea,Table Footnotec	Severity II^Table Footnoteb,Table Footnotec
Blindness	0.99 (1.29)	2.97 (1.81)	1.38 (0.72)	2.85 (0.97)
(N = 399)
Paralysis	3.29 (1.68)	4.07 (1.11)	1.87 (0.83)	3.00 (0.90)
(N = 399)
Allergy	0.96 (1.34)	1.51 (1.67)	1.08 (0.73)	1.77 (0.86)
(N = 393)

Notes:

a Unilateral blindness, paraplegia, or mild allergy;

b bilateral blindness, quadriplegia, or moderate allergy;

c significant difference (P < 0.05) across health scenarios.

Abbreviations: QALY, quality-adjusted life year; SD, standard deviation; TTO, time trade off; VAS, visual analog scale.

Table 3 WTP value for each health scenario (baht, rounded up/down in hundreds)

Health scenario	WTP value (baht), $\overline{X}$ (SD)
	Treatment		Prevention
	Severity I^Table Footnotea,Table Footnotec	Severity II^Table Footnoteb,Table Footnotec	Severity I^Table Footnotea,Table Footnotec	Severity II^Table Footnoteb,Table Footnotec
Blindness	99,600	154,000	19,000	31,100
(N = 399)	(131,400)	(197,500)	(34,800)	(77,000)
Paralysis	117,900	165,600	21,000	28,500
(N = 399)	(128,600)	(211,700)	(30,000)	(59,000)
Allergy	31,000	39,000	12,000	14,000
(N = 393)	(17,500)	(69,000)	(17,000)	(21,500)

Notes:

a Unilateral blindness, paraplegia, or mild allergy;

b bilateral blindness, quadriplegia, or moderate allergy;

c significant difference (P < 0.05) across health scenarios.

Abbreviations: SD, standard deviation; WTP, willingness to pay.

Table 4 WTP per QALY value (baht, rounded up/down in thousands)

	WTP per QALY (baht), $\overline{X}$(SD)
	Treatment		Prevention
	Severity I^Table Footnotea	Severity II^Table Footnoteb	Severity I^Table Footnotea	Severity II^Table Footnoteb
TTO
Blindness	285,000	185,000	137,000	113,000
(N = 399)	(488,000)	(465,000)	(330,000)	(662,000)
Paralysis	101,000	59,000	46,000	26,000
(N = 399)	(269,000)	(145,000)	(110,000)	(68,000)
Allergy	88,000	92,000	91,000	91,000
(N = 393)	(170,000)	(278,000)	(176,000)	(176,000)
VAS
Blindness	108,000	62,000	45,000	31,000
(N = 399)	(314,000)	(94,000)	(100,000)	(72,000)
Paralysis	79,000	63,000	31,000	26,000
(N = 399)	(114,000)	(95,000)	(72,000)	(45,000)
Allergy	41,000	28,000	41,000	27,000
(N = 393)	(71,000)	(57,000)	(76,000)	(51,000)

Notes:

a Unilateral blindness, paraplegia, or mild allergy;

b bilateral blindness, quadriplegia, or moderate allergy.

Abbreviations: QALY, quality-adjusted life year; SD, standard deviation; TTO, time trade off; VAS, visual analog scale; WTP, willingness to pay.

Table 5 Factors affecting WTP per QALY (baht, rounded up/down in thousands)

DV: Ln (WTP/QALY)^Table Footnotea	Treatment			Prevention
	β	SE (β)	P-value	β	SE (β)	P-value
Intercept	10.85	0.10	<0.001	10.08	0.10	<0.001
Monthly income (baht)	0.00002	2.6e-06	<0.001	0.00002	2.8e-06	<0.001
Gender
Male (ref)
Female	–0.32	0.08	<0.001	–0.23	0.09	0.013
Health Scenario
Blindness (ref)
Paralysis	–0.89	0.09	<0.001	–0.03	0.11	0.798
Allergy	–0.82	0.09	<0.001	–0.98	0.11	<0.001
Education
Primary school or lower (ref)
Secondary school	0.29	0.08	0.001	NA	NA	NA
Bachelor or higher	0.55	0.16	0.001	NA	NA	NA
	AIC = 7868.8			AIC = 7984.9

Note:

a Based on time trade off (TTO) method, as residuals were not normally distributed, so natural log transformations of WTP/QALY values were applied.

Abbreviations: AIC, Akaike’s information criterion; NA, not applicable; QALY, quality-adjusted life year; Ref, reference; SE, standard error; WTP, willingness to pay.