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Impact of inhaled corticosteroids on acute asthma hospitalization in Sweden |
Gerdtham U G, Hertzman P, Jonsson B, Boman G |
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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 Inhaled corticosteroids in the treatment of asthmatic patients.
Economic study type Cost-effectiveness analysis.
Setting Clinic. The economic study was carried out in Sweden.
Dates to which data relate The effectiveness and resource utilisation data were collected between 1978 and 1991 (except for 1984 in-patient care data which were not available). The price year was 1991.
Source of effectiveness data The evidence for the final outcomes was derived from a single study.
Link between effectiveness and cost data Costing was undertaken retrospectively on the same patient sample as that used in the effectiveness analysis.
Study sample Power calculations were not used to determine the sample size. The study sample was based on regional data from 14 health-care administrative regions covering6 million people (71% of the Swedish population).
Study design Retrospective cohort study. The sources of the required data were 14 health-care administrative regions.
Analysis of effectiveness The main outcomes were improved asthma control as measured by the number of bed-days per 1,000 inhabitants due to asthma, and sales of inhaled corticosteroids (as a measure of drug consumption) in terms of defined daily doses (DDDs). In the regression models analysed, asthma prevalence (as measured by the sales of inhaled bronchodilators) and the general trends in overall in-patient care (measured by the total number of bed-days in acute in-patient care) were included as the additional explanatory variables (as confounding variables). The validity of the raw data (up to 90%) was confirmed by another study.
Effectiveness results The number of bed-days due to acute asthma, in any of the 14 county councils included in the study, showed no change until 1985, after which there was a significant reduction (from 17-18 days to 9 days per 1,000 inhabitants in 1991). An exponential increase in the sales of corticosteroids occurred from 1978 to 1991 (from 3 DDDs per day per 1,000 inhabitants in 1985 to 12 DDDs per day per 1,000 inhabitants in 1991). Analysis by sub-groups in terms ofage and county council showed considerable variability. The regression analyses established a significant negative correlation between sales of inhaled corticosteroids and bed-days due to asthma (the coefficient varied between -2.14 and -0.90 in submodels) (P<0.01).
Clinical conclusions There is a significant inverse correlation between sales of inhaled corticosteroids and incidence of bed-days due to acute asthma, despite an increase in the prevalence of asthma.
Modelling In-patient care and drug sales data were incorporated into four different types of pooled cross-section time series regression models to investigate the relationship between the use of inhaled corticosteroids and the acute hospitalisation. The types of models adopted were two-way random-effect (county-specific effects and period-specific effects) models, one-way random-effect model, one-way fixed-effect model, and zero-factor model. The confounding variables controlled for were: differences in prevalence of acute asthma and overall trends in admissions and length of stay.
Measure of benefits used in the economic analysis The main benefit measure was improved asthma control, as measured by the number of bed-days per 1,000 inhabitants, in acute in-patient care due to asthma.
Direct costs Costs were not discounted. Quantities were not reported separately from the costs. The cost items were reported separately and were the average annual cost of inhaled corticosteroids, and the weighted average cost of a bed-day in acute somatic care (primarily internal medicine, including lung medicine and pediatrics). The perspective adopted in the cost analysis was that of the Swedish health care system. The unit costs ofitems included were reported separately. Resource utilisation data were obtained from the Swedish National Board of Health and Welfare covering all Swedish hospitals andthe National Corporation of Swedish Pharmacies. The date to which the price data referred was 1991.
Currency Swedish kroner (SEK). No conversion was carried out, however the 1991 exchange rate reported in the paper was US$1 = SEK6.2.
Sensitivity analysis One-way sensitivity analysis was carried out to test the sensitivity of results to bed-day costs.
Estimated benefits used in the economic analysis The number of bed-days due to acute asthma, in any of the 14 county councils included in the study, showed no change until 1985, after which there was a significant reduction (from 17-18 days to 9 days per 1,000 inhabitants in 1991). An exponential increase in the sales of corticosteroids occurred from 1978 to 1991 (from 3 DDDs per day per 1,000 inhabitants in 1985 to 12 DDDs per day per 1,000 inhabitants in 1991). Analysis by sub-groups in terms ofage and county council showed considerable variability.
Cost results The average annual cost of inhaled corticosteroids and the weighted average cost of a bed-day in acute somatic care were SEK2,620 and SEK2,640, respectively.
Synthesis of costs and benefits For every SEK1.0 spent on inhaled corticosteroids, there was an associated reduction of SEK1.5 (95%CI, 1.07-1.92) in hospital costs (based on the result of regression analysis) equivalent to SEK 3,934.
Authors' conclusions Clinical trial findings that treating asthmatic patients with inhaled corticosteroids improves asthma control and reduces the need for hospitalisation, seem to be realized in clinical practice. The increased costs of inhaled corticosteroids to the health-care system were more than offset by a reduction in the costs for acute somatic hospital care.
CRD COMMENTARY - Selection of comparators The study lacked a well-defined comparator against which the effects of the intervention (inhaled corticosteroids) could be properly assessed. Rather, the impact of increased corticosteroid use was implicitly compared with usage levels from the early 1980s.
Validity of estimate of measure of benefit The effectiveness results are likely to be internally valid given to the use of a large database, the raw data of which were validated up to 90% by another study. However, the effects of some confounding variables were not controlled for. Not all benefits associated with the use of the intervention were included in the analysis.
Validity of estimate of costs Adequate details of cost estimation were not given. The costs of adverse effects and indirect costs were not included.
Other issues The issue of generalisability to other settings or countries was not addressed.
Source of funding Supported by the Swedish Heart-Lung Foundation and Astra Draco.
Bibliographic details Gerdtham U G, Hertzman P, Jonsson B, Boman G. Impact of inhaled corticosteroids on acute asthma hospitalization in Sweden. Medical Care 1996; 34(12): 1188-1198 Indexing Status Subject indexing assigned by NLM MeSH Administration, Inhalation; Adrenal Cortex Hormones /administration & Aged; Asthma /drug therapy; Child, Preschool; Cross-Sectional Studies; Drug Utilization /trends; Hospitalization /economics /statistics & Humans; Infant; Models, Statistical; Regression Analysis; Retrospective Studies; Sweden; dosage; numerical data AccessionNumber 21997008017 Date bibliographic record published 31/03/1999 Date abstract record published 31/03/1999 |
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