Cost-minimization analysis of sublingual immunotherapy versus subcutaneous immunotherapy for house dust mite respiratory allergic disease in Denmark

Figures & data

Table 1. General model assumptions.

Assumptions	Details
General
Discount rate	According to Danish guidelines, the discount rate is 3%^14^,^15.
Patient costs	Patient costs include travel cost (10 km per visit) and lost wages (2 h per visit).**
	SQ SLIT-tablet	SQ SCIT
Duration of treatment	All patients are treated for 3 years.*	80% of the patients are treated for 3 years and 20% of the patients are treated for 5 years.*
Immunotherapy treatment and visits	Year 1: treatment is initiated by two consultations, i.e., the administration of first tablet in the clinic, and investigation of desired treatment effect ∼1 month later. Initial consultations are followed by an additional follow-up consultation. Years 2 and 3: two follow-up consultations per year^16.	Treatment is initiated with 15 weekly consultations. This is followed by a transition phase with one consultation 2 weeks after the last up-titration consultation and an additional consultation 4 weeks after the first transition consultation. After the transition phase, maintenance consultations occur with 8-week intervals^16.
Treatment setting	25% of the initial visits are carried out by a general practitioner, 10% are carried out by a medical specialist in a hospital on an outpatient basis, and 65% are carried out by a medical specialist in a private clinic (specialists in internal medicine: 50%, specialists in otolaryngology: 50%). The distribution of follow-up visits are 40% at general practitioners, 5% by a medical specialist in a hospital on an outpatient basis, and 55% by a medical specialist in a private clinic^16.	20% of the up-dosing visits are carried out by a general practitioner, 60% are carried out by a medical specialist in a private clinic, and 20% are carried out by a medical specialist in a hospital on an outpatient basis; 20% of the maintenance visits are carried out at a general practitioner, 60% are carried out by a medical specialist in a private clinic, and 20% are carried out by a medical specialist in a hospital on an outpatient basis^16.
Additional medical supervision	No peak flow measurements are carried out.*	Peak flow measurements are carried out before and after each injection.*
Compliance	Compliance is 80%.*	Compliance is 100% in the up-dosing phase and 90% in the maintenance phase.*
Tablets/Vials	The purchase of tablets is calculated according to the best fit of the remaining treatment resulting in as little waste as possible of the last package.	Vials are personal. A maintenance vial contains 5 mL and 4.7 injections can be extracted from each vial. Any remaining liquids in the titration kit after the up-dosing injections are used in the maintenance phase.*
Treatment of second allergy	Patients who are treated for both HDM- and grass allergy have an additional start-up visit.	50% of physicians treating patients for two allergies treat for both allergies at the same consultation. The remaining 50% initiate the treatment of the second allergy after the up-dosing phase of the first treatment. When injections are given at the same consultation the second injections are given 30 minutes after the first.*

*The compliance rates are based on assumptions.

**10 km per visit and 2 h per visit based on experiences on daily practice in Denmark.

Table 2. Average resource use for treatment of a patient with HDM RAD.

Resource category	Resource type	Year 1	Year 2	Year 3	Year 4	Year 5
SQ SLIT-tablet
Medication	Number of tablets^a	292	292	292	—	—
Physician	Number of initial visits^b	2	—	—	—	—
	Treatment by general practitioner (visits)	0.50	—	—	—	—
	Treatment by medical specialist (visits)	1.30	—	—	—	—
	Treatment in hospital (visits)	0.20	—	—	—	—
	Number of follow-up visits^c	1	2	2	—	—
	Treatment by general practitioner (visits)	0.40	0.80	0.80	—	—
	Treatment by medical specialist (visits)	0.55	1.10	1.10	—	—
	Treatment in hospital (visits)	0.05	0.10	0.10	—	—
Patient	Total time spent (hours)^d	6	4	4	—	—
	Travel distance (km)^e	30	20	20	—	—
SQ SCIT
Medication	Number of up-titration kits	1	—	—	—	—
	Number of maintenance vials needed^f	1	2	1	1	—
Physician	Up-titration injections (visits)	15	—	—	—	—
	Treatment by general practitioner (visits)	0.8	—	—	—	—
	Treatment by medical specialist (visits)	11.3	—	—	—	—
	Treatment in hospital (visits)	3.0	—	—	—	—
	Maintenance injections (visits)	5.4	5.9	5.9	5.9	2.2
	Treatment by general practitioner (visits)	1.1	1.2	1.2	1.2	0.4
	Treatment by medical specialist (visits)	3.2	3.5	3.5	3.5	1.3
	Treatment in hospital (visits)	1.1	1.2	1.2	1.2	0.4
	Number of peak flow measurements	40.8	11.7	11.7	11.7	4.3
Patient	Total time spent (hours)^d	40.8	11.7	11.7	11.7	4.3
	Travel distance (km)^e	204.0	58.5	58.5	58.5	21.5

a One tablet/day; compliance = 80%;

b two initial visits;

c One follow-up visit 1^st year; 2 follow-up visits the following years;

d 2 h/visit based on experiences on daily practice in Denmark;

e 10 km/visit based on experiences from daily practice in Denmark;

f number of maintenance visits (injections)/number of injections per maintenance vial; i.e., number of maintenance visits (injections)/4.7; Remaining injections in opened vial at the end of the year are used in the following year.

Table 3. Unit costs (€).

Cost category	Cost type	Unit	€/unit	Source
Medication
SQ SLIT-tablet	Pack with 30 tablets	Pack	97.8	www.medicinpriser.dk^19
	Pack with 90 tablets	Tablet	286.4	www.medicinpriser.dk^19
SQ SCIT	Titration kit, Mite	Titration kit	265.7	www.medicinpriser.dk^19
	Maintenance vial, Mite	Vial (5 mL)	230.7	www.medicinpriser.dk^19
Physician visits
General practitioners	Visit	Visit	18.3	www.laeger.dk^20
	Peak flow measurement	Measurement	5.1	www.laeger.dk^20
Medical specialist,	First visit	Visit	82.9	www.laeger.dk^20
Internal medicine	Second visit	Visit	59.1	www.laeger.dk^20
	Subsequent visit	Visit	19.5	www.laeger.dk^20
	Allergy injection – 1^st allergen	Injection	41.4	www.laeger.dk^20
	Allergy injection – subsequent allergen	Injection	16.6	www.laeger.dk^20
	Lung functions test	Test	82.8	www.laeger.dk^20
Medical specialist,	First visit	Visit	81.8	www.laeger.dk^20
Otorhinolaryngologist	Second visit	Visit	45.0	www.laeger.dk^20
	Subsequent visit	Visit	21.9	www.laeger.dk^20
	Allergy injection – 1^st allergen	Injection	0.0	www.laeger.dk^20
	Allergy injection – subsequent allergen	Injection	0.0	www.laeger.dk^20
	Peak flow measurement	Measurement	0.0	www.laeger.dk^20
	Lung functions test	Test	0.0	www.laeger.dk^20
Hospital	Outpatient visit	Visit	102.8	www.drg.dk^21
	Additional costs, uncomplicated allergy treatment	Visit	128.9	www.drg.dk^21
Patient costs
Work	Productivity loss/foregone earnings^a	Hour	41.7	www.statistikbanken.dk^22
Travel	Travel by private car	Km	0.5	www.skat.dk^23

2015-price level.

a Productivity loss/foregone earnings are based on the mean salary/hours for the general population aged 18–65 years in Denmark, including the unemployed.

Table 4. Cost of treatments for HDM RAD with SQ SLIT-tablet and SQ SCIT (€).

Cost category	Cost type	Year 1	Year 2	Year 3	Year 4	Year 5	PV
SQ SLIT-tablet
Treatment costs	Medication	1146	1146	580	—	—	2804
	Physician start-up visits, total	143	—	—	—	—	143
	Treatment by GP	9	—	—	—	—	9
	Treatment in private clinic	87	—	—	—	—	87
	Treatment in hospital	46	—	—	—	—	46
	Physician follow-up visits, total	30	61	61	—	—	146
	Treatment by GP	7	15	15	—	—	35
	Treatment in private clinic	11	23	23	—	—	55
	Treatment in hospital	12	23	23	—	—	56
Total treatment costs		1319	1206	640	—	—	3094
Patient costs	Travel expenses	15	10	10	—	—	34
	Productivity loss/Foregone earnings	250	167	167	—	—	570
Total costs		1584	1383	817	—	—	3697
SQ SCIT
Treatment costs	Medication (titration kits)	266	—	—	—	—	266
	Medication (vials)	231	461	231	46	—	938
	Physician up-dosing injections, total	1209	—	—	—	—	1209
	Treatment by GP	86	—	—	—	—	86
	Treatment in private clinic	429	—	—	—	—	429
	Treatment in hospital	695	—	—	—	—	695
	Physician maintenance visits, total	415	450	450	90	30	1385
	Treatment by GP	31	33	33	7	2	103
	Treatment in private clinic	134	145	145	29	10	448
	Treatment in hospital	250	271	271	54	18	835
Total treatment costs		2121	911	681	136	30	3799
Patient costs	Travel expenses	101	29	29	6	2	164
	Productivity loss/Foregone earnings	1703	488	488	98	32	2755
Total costs		3925	1429	1198	240	71	6717

2015-price level. PV, present value (future costs beyond the first year discounted to present value).

Figure 1. Relationship between number of patients treated, potential treatment cost savings and potential additional patients treated, HDM RAD. PV, present value.

Table 5. Univariate sensitivity analysis for HDM RAD (direct treatment costs in €).

Sensitivity analyses	Direct treatment costs (€) for SQ SLIT tablet, PV	Direct treatment costs (€) for SQ SCIT, PV	Difference from SQ SLIT tablet, PV
General
Base case	3094	3799	+705
Discount rate
1%	3141	3851	+711
5%	3048	3749	+700
SQ SLIT-tablet
Initiation of treatment
100% hospital setting	3414	3799	+384
100% general practice	2987	3799	+811
100% medical specialists	3085	3799	+713
Follow-up treatment
100% hospital setting	4066	3799	−267
100% general practice	3036	3799	+763
100% medical specialists	3047	3799	+751
Number of visits per year
4 + 3+3	3182	3799	+617
2 + 1+1	3005	3799	+793
Compliance
100%	3744	3799	+55
60%	2345	3799	+1454
SCIT
Injections per vial
4.5	3094	3880	+787
4.9	3084	3807	+713
Up-titration visits
100% hospital setting	3094	6065	+2971
100% general practice	3089	3017	−76
100% medical specialists	3089	3304	+210
Maintenance visits
100% hospital setting	3094	6586	+3493
100% general practice	3094	2928	−166
100% medical specialists	3094	3160	+66
Number of weeks between injections
10 weeks	3094	3313	+220
6 weeks	3094	4473	+1380
Compliance, up-titration
80%	3094	3568	+474
Compliance, maintenance
100%	3094	4024	+931
60%	3094	3136	−42
Duration of treatment
100% treated for 3 years, 0% for 5 years	3094	3648	+554
60% treated for 3 years, 40% for 5 years	3094	2491	−560

2015-price level. PV, present value.

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