Estimation of the value of convenience in taking influenza antivirals in Japanese adult patients between baloxavir marboxil and neuraminidase inhibitors using a conjoint analysis

Figures & data

Figure 1. Example of choice task questions in the survey for the conjoint analysis.

Table 1. Attributes and attribute levels in the survey for the conjoint analysis.

Attribute	Level
Administration route	Oral/inhalant
Duration of administration	1 day/5 days/10 days
Frequency of administration per day	Once/twice/thrice
Out-of-pocket expenses	JPY 3,000/JPY 6,000/JPY 9,000/ JPY 12,000

Abbreviation. JPY: Japanese yen ($1.00 corresponds to approximately JPY 105.00 as of August 2020).

Table 2. Number of respondents by age and gender.

Age (5-year periods; years)	Male	Female	Total
20–24	118	100	218
25–29	207	212	419
30–34	134	145	279
35–39	231	224	455
40–44	167	237	404
45–49	231	223	454
50–54	160	171	331
55–59	164	152	316
60–64	138	123	261
Total	1,550	1,587	3,137

Table 3. Number of respondents by dosage forms after cross-tabulation based on answers to questions (Q5) “Which type of antiviral agent did you take the last time?” and (Q6) “What kind of dosage did you take of (or how to use) the antiviral agent?”

	Oral drugs	Inhalants	Total
Once	579	916	1,495
Twice a day, 5 days	908	266	1,174
Not sure	229	113	342
Total	1,716	1,295	3,011

Note: Respondents who answered as “not sure” to Q5 are excluded. The questions and choices are shown in Table S1.

Figure 2. Utility of each variable based on the baseline model.

Table 4. Monetary value of each level of each attribute estimated by the baseline model.

	Estimate	SE	p-Value	Monetary value (95% CI)
Inhalant	0.000
Oral	0.221	0.014	<.001	JPY 741 (652–830) discount
1 day	0.000
5 days	−0.619	0.016	<.001	JPY 2,072 (1,967–2,177) increase
10 days	−1.245	0.018	<.001	JPY 4,172 (4,056–4,288) increase
Once a day	0.000
Twice a day	−0.171	0.017	<.001	JPY 574 (462–686) increase
Thrice a day	−0.337	0.016	<.001	JPY 1,129 (1,021–1,237) increase
JPY 3,000	0.000
JPY 6,000	−0.896	0.020	<.001
JPY 9,000	−1.673	0.021	<.001
JPY 12,000	−2.618	0.025	<.001

Abbreviations. JPY, Japanese yen ($1.00 corresponds to approximately JPY 105.00 as of August 2020); CI, confidence interval; SE, standard error.

Figure 3. Difficulty in taking the drug (answer to Q 8-1: “Was it easy to take the antiviral that you took the last time?”) (A), and reasons for the difficulty (answer to Q 8-2: “Why did you answer ‘Neither’ or ‘No’ to Q8-1 regarding the ease of taking the antiviral that you took the last time?”) by type of drug (B). Multiple choices were allowed. Denominator: All respondents according to the type of dosage form of the drugs.

Figure 4. Feeling of worry about taking the drug (answer to Q 9: “When you were taking the antiviral for influenza the last time, were you worried that you would vomit out the drugs or you did not take (inhale) enough of the drugs?”) by type of dosage form of the drugs (A) or by age and gender (B).

Figure 5. Number of days to fever resolution from initiation of the antivirals (answer to Q 10: “When you were taking the antiviral for influenza the last time, how long did it take to break your fever after the first dose?”) by dosage form of the drugs identifying the percentages of respondents excluding those who answered “not sure” for each answer. N: number of respondents excluding “not sure” (oral, single dose: 55; oral, 5-day dose: 82; inhalant, single dose: 98, and inhalant, 5-day dose: 19).

Figure 6. Number of days to return to the usual life from initiation of the antivirals (answer to Q 11: “When you were taking the antiviral for influenza the last time, how long did it take to return to your usual life (working or attending school) after the first dose?”) by type of dosage form of the drugs identifying the percentages of respondents excluding those who answered “not sure” for each answer. N: number of respondents excluding “not sure” (oral, single dose: 47; oral, 5-day dose: 60; inhalant, single dose: 86, and inhalant, 5-day dose: 12).

Table 5. Estimated total cost of the drug, utility, and productivity loss for influenza per patient for available antivirals in Japan.

	Baloxavir marboxil	Oseltamivir	Oseltamivir (generic)	Laninamivir	Zanamivir
Dosage form	Oral, single dose	Oral, 5-day dose		Inhalant, single dose	Inhalant, 5-day dose
1) Given: drug cost per patient (adult)	JPY 4,878*	JPY 2,672	JPY 1,281	JPY 4,359	JPY 2,882
2) Total value of utility estimated by conjoint analysis	JPY 3,387	JPY 741	JPY 741	JPY 2,646	JPY 0
Value of oral compared with inhalant	JPY 741	JPY 741	JPY 741	JPY 0	JPY 0
Value of 1 day dosing compared with the 5-day dose	JPY 2,072	JPY 0	JPY 0	JPY 2,072	JPY 0
Value of once a day compared with twice a day	JPY 574	JPY 0	JPY 0	JPY 574	JPY 0
3) Consideration: productivity loss	JPY 46,816	JPY 52,812	JPY 52,812	JPY 50,227	JPY 52,572
Average number of days to return to usual life (working or attending school) from the survey	4.63	5.22	5.22	4.97	5.20
Productivity loss per day	JPY 10,116	JPY 10,116	JPY 10,116	JPY 10,116	JPY 10,116
Total cost of influenza	JPY 48,306	JPY 54,743	JPY 53,352	JPY 51,940	JPY 55,454
1) − 2) + 3)
Difference from baloxavir marboxil	–	JPY 6,436	JPY 5,045	JPY 3,634	JPY 7,148

*Note: The drug cost of baloxavir marboxil was calculated for the prescription dosage of 40 mg (for patients weighing <80 kg) based on the average body weight of the Japanese people. All drugs not specified as “generic” are branded drug.