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A randomised controlled trial to assess the relative benefits of large volume spacers and nebulisers to treat acute asthma in hospital |
Dewar A L, Stewart A, Cogswell J J, Connett G J |
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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 Two health technologies for the treatment of childhood asthma through the administration of beta-2 agonists were considered in the study: a metered dose inhaler and large volume spacer was compared with conventional nebulisers.
Economic study type Cost-effectiveness analysis.
Study population The study population comprised children aged three years or over who required hospital admission for acute asthma. Children were excluded if they were unable to use a spacer mouthpiece, presented with severe symptoms requiring intravenous treatments, or were readmitted during the study period.
Setting The setting was a hospital. The study was carried out at Southampton University Hospital, Southampton, and Poole District General Hospital, Dorset, UK.
Dates to which data relate The dates during which the data concerning the effectiveness evidence and the resource use were collected were not reported. The price year was not reported.
Source of effectiveness data The effectiveness evidence was derived from a single study.
Link between effectiveness and cost data The costing was undertaken prospectively on the same patient sample as that used in the effectiveness analysis.
Study sample Power calculations were not performed, but the sample size was determined using estimations from asthma admission data over the previous two years at the two centres. As a result, a total of 100 patients was considered reasonable over the study period (five months). All eligible children were invited to participate in the study and 78 patients were enrolled. 7 children were excluded because they required intravenous treatment (2 before and 5 after randomisation) and 9 children were excluded because they were readmitted during the study period.
Overall, 62 children were evaluated for the analysis:
33 patients (mean age: 8 years, male: 24) remained in the nebulisers group receiving salbutamol 5 mg up to one hourly by jet nebulisers driven by oxygen at 6-8 l/min,
and 29 patients (mean age: 6.9 years, male: 16) were assigned to the spacer group receiving salbutamol 100 microg by large volume spacer, up to 10 puffs one hourly.
Study design The study was an open, randomised, controlled trial, carried out in two centres. Children were randomly allocated to one of the two groups using sequential pre-sealed envelopes. Patients were followed for two weeks after discharge and contacted by telephone. No loss to follow-up was reported. Children were then further followed for 12 months to assess the readmission rate.
Analysis of effectiveness The analysis of effectiveness was based on treatment completers only because the authors decided to exclude those children requiring intravenous treatment. The primary health outcomes used in the effectiveness analysis were the length of the hospital stay, the rate of readmission, and the morbidity scores, obtained by completion of the Index of Perceived Symptoms questionnaire. The questionnaire was developed in 1990 specifically for children with asthma and gives scores for daytime, night time, and disability. No statistically significant difference was found in terms of demographics or clinical characteristics between the study groups.
Effectiveness results The median length of hospital stay was 40 hours for the nebulisers group and 36.5 hours for the spacer group, but the difference did not reach statistical significance. However, interquartile ranges indicated a trend to shorter admission times in the spacer group.
The readmission rates after 12 months were 27.2% in the nebulisers group and 13.8% in the spacer group.
With respect to morbidity scores, the median daytime score (basic range from 4 to 20) was 10 (range: 4 - 17) in the nebulisers group and 6 (range: 4 - 14) in the spacer group, (p=0.001);
the median night time score (basic range from 2 to 20) was 4 (range: 2 - 10) in the nebulisers group and 3 (range: 2 - 6) in the spacer group, (p<0.05); and
the median disability score (basic range from 5 to 25) was 8 (range: 5 - 19) in the nebulisers group and 6 (range: 5 - 16) in the spacer group, (p>0.05).
Clinical conclusions Spacer devices were more effective than conventional nebulisers in reducing asthma morbidity, as shown by the questionnaire results. There was also a favourable trend for spacer devices in reducing hospital stay and readmissions.
Measure of benefits used in the economic analysis Health outcomes were left disaggregated and no summary benefit measure was used in the economic analysis, therefore a cost-consequences analysis was carried out.
Direct costs Discounting was not relevant given that the time horizon of the study was 5 months. Unit costs and quantities of resources used were not reported. The resource/cost boundary appeared to be that of the hospital. The analysis of costs included the fixed cost of disposable nebuliser equipment and variable costs of salbutamol nebules and prednisolone in the nebulisers group, and the fixed price of a metered dose inhaler and volumatic spacer, together with prednisolone (inpatient) and the additional course of prednisolone for future use at home in the spacer group. The cost of oxygen was not included. The estimation of the costs was presumably based on actual data derived from the hospital finance department, but this is not recorded. The dates during which the resource use data were collected were not reported. The price year was not reported.
Statistical analysis of costs Independent sample t-test was carried out.
Indirect Costs Indirect costs were not included.
Sensitivity analysis No sensitivity analysis was carried out.
Estimated benefits used in the economic analysis Please refer to the effectiveness results reported earlier.
Cost results The costs per patient amounted to 20.25 in the nebulisers group and 5.43 in the spacer group. The difference was statistically significant, (p<0.001).
Synthesis of costs and benefits Authors' conclusions The authors concluded that spacer devices proved to be not only as safe as conventional nebulisers but also more effective, because children in the spacer group showed a significant improvement in their symptoms at two weeks. In addition, spacer devices appeared to be less expensive than conventional nebulisers. The estimated cost savings for a district hospital treating 200 children would be about 3,000.
CRD COMMENTARY - Selection of comparators The choice of health technologies compared in the study was clearly determined by the selection of the intervention used in current practice (conventional nebulisers) and the innovative and effective, but not widely used treatment (spacer device). You should consider whether these represent currently used technologies in your own setting.
Validity of estimate of measure of effectiveness The validity of the effectiveness analysis is likely to be high given the randomisation process used, although blinding was difficult to achieve due to the nature of the devices. Furthermore, appropriate statistical analyses were carried out to show the comparability of the two study groups at baseline. The study sample appeared to be quite representative of the study population. However, the analysis of the effectiveness was not conducted on an intention to treat basis and the sample size was somewhat small.
Validity of estimate of measure of benefit No summary benefit measure was used in the economic analysis, and therefore a cost-consequences analysis was conducted. It would have been helpful had the health impact of the intervention (already measured through the morbidity scores) been better specified and combined with the costs of the treatments.
Validity of estimate of costs The cost analysis included only direct costs related to the use of the devices. The estimation of the costs appeared to be quite specific to the study setting and difficult to generalise to different settings. The perspective of the analysis was not indicated clearly and the price year was not reported. It would have been interesting had the authors adopted a societal perspective that included indirect costs (such as productivity losses borne by the parents of the children) due to the trend towards a shorter hospital stay in the spacer group compared to the nebulisers group.
Other issues The authors compared their results with those from other studies and their findings appeared to be consistent with the published literature. The issue of the generalisability of the study to other settings was not addressed and sensitivity analyses were not carried out. Therefore, the external validity of the study may be somewhat limited.
Implications of the study The authors highlighted the difficulty of "reversing the nebulisers culture" in the two centres where the study was carried out. However, after observing the advantages of spacer devices, both the hospitals decided to use metered dose inhalers and spacers as first line treatment for children with acute asthma. Future research should be based on studies involving a larger sample size than the present study to better assess the cost-effectiveness of spacer devices.
Bibliographic details Dewar A L, Stewart A, Cogswell J J, Connett G J. A randomised controlled trial to assess the relative benefits of large volume spacers and nebulisers to treat acute asthma in hospital. Archives of Disease in Childhood 1999; 80(5): 421-423 Indexing Status Subject indexing assigned by NLM MeSH Acute Disease; Adolescent; Adrenergic beta-Agonists /administration & Albuterol /administration & Asthma /drug therapy; Bronchodilator Agents /administration & Child; Child, Preschool; Drug Costs; Female; Hospitalization; Humans; Length of Stay; Male; Nebulizers and Vaporizers; dosage /economics; dosage /economics; dosage /economics AccessionNumber 21999000998 Date bibliographic record published 31/07/2002 Date abstract record published 31/07/2002 |
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