|
Health-economic analyses of subcutaneous specific immunotherapy for grass pollen and mite allergy |
Petersen K D, Gyrd Hansen D, Dahl R |
|
|
Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. Health technology The study compared treatment with specific immunotherapy (SIT) with symptomatic treatment or standard care amongst patients with grass pollen or mite allergy.
Economic study type Cost-effectiveness analysis.
Study population The study population comprised 16- to 60-year-old patients who had started SIT during the study period.
Setting The setting was outpatient secondary care. The economic study was undertaken in Aarhus, Denmark.
Dates to which data relate The effectiveness data were derived from patients who received SIT between 1 January 1996 and 1 January 2002. Resource use appears to have been derived between 1 January 1997 and 1 February 2003. The price year was 2002.
Link between effectiveness and cost data The costing was undertaken retrospectively on the same patient sample as that used in the effectiveness study. However, in order to obtain information on medicine consumption before patients commenced their treatment with SIT, a different cohort of 53 patients who started SIT for either grass pollen or mite allergy during 1 November 2002 and 1 February 2003 was used.
Study sample No sample size, to assure a certain power, appears to have been determined in the planning phase of the study. A total of 253 patients who started SIT during 1 January 1996 and 1 January 2002 were retrospectively enrolled in the study from the Allergy Unit at Aarhus University Hospital and from a specialist practice in Aarhus. All enrolled patients received a questionnaire to determine the effectiveness of SIT. Two hundred and four patients (81%) completed and returned the questionnaire.
Study design The study design was a within-group comparison that was undertaken at two outpatient centres in Aarhus, Denmark. The questionnaire asked patients to describe whether they had experienced a change in their quality of well-being in connection with SIT. The follow-up time ranged from 1 to 7 years.
Analysis of effectiveness The primary health outcome used was the change in quality of well-being associated with SIT. The quality of well-being was measured on a 5-point scale in which patients reported whether they thought their well-being had improved a lot, a little, not change, or been aggravated a lot, or a little. The patients were also asked to report whether they thought the advantages of SIT were greater than the disadvantages.
Effectiveness results Seventy-five per cent of patients (95% confidence interval, CI: 69 to 80) found that the advantages of SIT outweighed the disadvantages.
A total of 67.2% of vaccinated patients experienced improvements in their psychological well-being, with 39.7% of respondents stating it had improved a lot and 27.5% reporting it had improved a little.
A total of 27.5% of patients reported that their well-being was unchanged, while 4.4% reported that it was aggravated a little and 1% that it was aggravated a lot.
Clinical conclusions The clinical evaluation suggested that a majority of patients found that treatment with SIT improved their quality of well-being in comparison with standard care.
Modelling The authors reported that evidence from the literature suggested that the effects of SIT lasted 3 to 6 years after 3 years of treatment. Consequently, the authors extrapolated the effectiveness results for SIT to a period of 5 years.
Measure of benefits used in the economic analysis The measure of health benefit used was the number of patient-years in which psychological well-being was improved. Since the outcomes could be incurred over a 9-year period, discounting was relevant and was appropriately undertaken at an annual rate of 5%.
Direct costs The direct costs included in the analysis were those to the patient and health care system. Such costs were for medication, visits to medical doctors, visits to the emergency departments and hospital length of stay, and transportation. Resource use for SIT medication was obtained from the National Health Service in Aarhus County; resource use for pre-SIT medication was derived from a cohort of patients receiving SIT between 1 November 2002 and 1 February 2003. Medicines were then costed using pharmacy recommended retail prices. Information on visits to general practitioners and specialists was obtained from the local county authorities of Aarhus. However, this registry did not cover visits for the 26 patients who initiated SIT in 1996. The unit prices for medical visits were derived from National Health Service fees. Visits to the emergency department and hospital length of stay were derived from the patient questionnaire used to determine effectiveness. The costs were estimated using the Diagnosis-Related Group rate. Finally, patients were also asked in the questionnaire to report the number of kilometres they had travelled to receive SIT. Each kilometre was costed at the Danish mileage allowance.
Since the costs could be incurred over a 9-year period, all future costs were appropriately discounted at an annual rate of 5%. All costs were appropriately inflated to 2002 prices. The study reported the average costs. The resources used and costs were not reported separately.
Statistical analysis of costs The costs were treated as point estimates (i.e. the data were deterministic).
Indirect Costs The productivity costs included in the study were the costs due to foregone work or leisure whilst attending vaccination, and the costs due to sick days. The questionnaire asked patients to specify how much leisure or work time they had lost when attending vaccinations and/or due to sickness. Hours of leisure and work were assigned values equivalent to net income as reported in Denmark's Statistics. The authors' argument for valuing leisure and work equally was that individuals choose to work until the value of their time equals the compensation they receive from working. Leisure or work time foregone was obtained from patients enrolled in the study who received SIT between 1 January 1996 and 1 January 2002.
Since the costs could be incurred over a 9-year period, all future costs were appropriately discounted at an annual rate of 5%. All costs were appropriately inflated to 2002 prices. The study reported the average costs. The resources used and costs were not reported separately.
Sensitivity analysis The authors did not undertake any statistical or sensitivity analysis on the outcome or cost data.
Estimated benefits used in the economic analysis See the 'Effectiveness Results' section.
Cost results From a health care perspective, the average total discounted costs were DKK 1,964 before SIT (i.e. the period when patients received standard care) and DKK 944 after SIT.
The average discounted direct costs incurred by the patients were DKK 616 before SIT and DKK 128 after SIT.
The average total discounted costs incurred by society were DKK 16,285 before SIT and DKK 3,570 after SIT.
Synthesis of costs and benefits The costs and benefits were combined using an incremental cost-effectiveness ratio (ICER; i.e. the additional cost per additional improvement in psychological well-being). The authors only used direct costs for this analysis and did not include productivity costs.
The authors reported the ICERs in a figure, which makes it difficult to report the exact ICERs here.
During the first year after the start of SIT, the ICER was approximately DKK 16,000. Nine years after the start of SIT, the ICER was somewhere between DKK 2,000 and 3,000.
Authors' conclusions Compared with standard care, specific immunotherapy (SIT) was associated with initial resource investments and subsequent resource savings in the long term.
CRD COMMENTARY - Selection of comparators A justification was given for the comparator used. It represented current practice in the authors' settings. You should decide if the comparator represents current practice in your own setting.
Validity of estimate of measure of effectiveness The study design was a within-group comparison in which patients were asked, amongst other things, to compare treatment with SIT with standard care by asking them if their quality of well-being had improved after SIT treatment. The problem with this study design is that external factors might have affected the authors' results. For example, through the passage of time patients might have forgotten the effects of previous treatment on their own health, or the patients' current situation might affect their quality of well-being, irrespective of treatment. The study sample was representative of the study population. The nature of the study design used represents a limitation to the internal validity of the study as external factors might have influenced the effectiveness results. Further, the authors did not report 95% confidence intervals alongside the proportion of patients reporting improved outcomes after treatment with SIT.
Validity of estimate of measure of benefit The estimation of health benefit (patient-years in which psychological well-being was improved) was obtained directly from the effectiveness study. The use of this outcome, however, will hinder comparisons with the outcomes of other interventions. The authors extrapolated the effectiveness results over a 5-year period but provided very few details of how this was done. The authors reported that a cost-effectiveness analysis and cost-benefit analysis were performed. However, they did not convert health outcomes into monetary values (e.g. derive a willingness-to-pay estimate for a 1-year increase in quality of well-being).
Validity of estimate of costs The analysis of the costs was performed from a societal perspective. It appears that all the relevant categories of costs, and all costs relevant to each category, have been included in the analysis. Resource use was derived from the patients' questionnaires, experiences of other patient cohorts, and administrative databases. All sources of resource use were appropriately reported and described. The unit costs were also derived from a variety of sources, mainly those of official national and local statistics. As with resource use, all sources were appropriately reported. Since the costs were incurred during a 5-year period, discounting was relevant and was appropriately performed. However, the authors did not perform any statistical or sensitivity analysis to allow for uncertainty and variability. The price year was reported, which will aid any further inflation exercises.
Other issues The authors reported that few studies had addressed the economic outcomes of SIT. The generalisability to other settings was not addressed. The authors do not appear to have presented their results selectively, although they did not report the results of statistical or sensitivity analyses. The authors' conclusions reflected the scope of the analysis, and they appropriately reported and highlighted the study's limitations. For example, the study design was subject to a time delay because of a potential recall bias, which could under or overestimate the effects of SIT. Also, effects could be biased by the fact that the study included no control group (placebo effect).
Implications of the study The authors would appear to recommend the use of SIT treatment as it increased societal welfare.
Bibliographic details Petersen K D, Gyrd Hansen D, Dahl R. Health-economic analyses of subcutaneous specific immunotherapy for grass pollen and mite allergy. Allergologia et Immunopathologia 2005; 33(6): 296-302 Other publications of related interest Because readers are likely to encounter and assess individual publications, NHS EED abstracts reflect the original publication as it is written, as a stand-alone paper. Where NHS EED abstractors are able to identify positively that a publication is significantly linked to or informed by other publications, these will be referenced in the text of the abstract and their bibliographic details recorded here for information.
Kozma CM, Sadik MK, Watrous ML. Economic outcomes for the treatment of allergic rhinitis. Pharmacoeconomics 1996;10:4-13.
Jarolim E, Poulsen LK, Stadler BM, et al. A long-term follow-up study of hyposensitization with immunoblotting. J Allergy Clin Immunol 1990;85:996-1004.
Indexing Status Subject indexing assigned by NLM MeSH Absenteeism; Adolescent; Adult; Allergens /adverse effects /immunology /therapeutic use; Animals; Antigens, Plant /adverse effects /drug effects /immunology /therapeutic use; Cost-Benefit Analysis; Denmark /epidemiology; Desensitization, Immunologic /economics; Drug Costs; Female; Hospital Costs; Hospitals, University; Humans; Leisure Activities; Male; Middle Aged; Mites /immunology; Poaceae; Pollen /adverse effects /immunology; Private Practice; Rhinitis, Allergic, Perennial /economics /epidemiology /therapy; Rhinitis, Allergic, Seasonal /economics /epidemiology /therapy; Surveys and Questionnaires; Transportation of Patients /economics AccessionNumber 22006006378 Date bibliographic record published 31/07/2007 Date abstract record published 31/07/2007 |
|
|
|