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Effect and offset of effect of treatments for hip fracture on health outcomes |
Jonsson B, Kanis J, Dawson A, Oden A, Johnell O |
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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 The authors evaluated two hypothetical interventions to prevent hip fracture in the overall female population and in a high-risk female population. For one intervention the authors assumed treatment costs approximating treatment with bisphosphonates, and for the other intervention the authors assumed treatment costs approximating those of hormone replacement therapy (HRT).
Type of intervention Primary and secondary prevention.
Study population Two populations were evaluated. The first was the general female population of women aged between 50 and 80 years, the second was a female population with a two-fold increase in risk of hip fracture.
Setting The setting was the community. The economic study was conducted in Sweden.
Dates to which data relate Effectiveness evidence was based on the authors' assumptions, and dates were therefore not provided. Resources and price data were taken from publications published in 1997 and 1998.
Source of effectiveness data Effectiveness data were based on the authors' assumptions.
Link between effectiveness and cost data Modelling A Markov model was used to synthesise cost and effectiveness data and to explore a range of values concerning the duration of treatment effect.
Outcomes assessed in the review The outcome assessed was the reduction of risk of hip fracture following five years' treatment with bisphosphonates or hormone replacement therapy (HRT).
Study designs and other criteria for inclusion in the review Sources searched to identify primary studies Criteria used to ensure the validity of primary studies Methods used to judge relevance and validity, and for extracting data Number of primary studies included Two studies were identified for data on the treatment effectiveness of the bisphosphonates and one study was identified for data for the effectiveness of HRT.
Methods of combining primary studies Primary studies were not combined.
Investigation of differences between primary studies Results of the review The authors stated that the studies identified in the review justified the assumptions that intervention with bisphosphonates and HRT may be set to 50% hip fracture risk reduction.
Methods used to derive estimates of effectiveness The estimate of treatment effectiveness was based on the authors' assumptions.
Estimates of effectiveness and key assumptions The authors assumed that both the hypothetical interventions (bisphosphonate and HRT) reduced the risk of hip fracture by 50%.
Measure of benefits used in the economic analysis The outcome measure used in the economic analysis was quality-adjusted life years saved (QALYs). The authors reported that EuroQoL (EQ-5D) was used to derive the health state utilities, and these were matched for age. It is not clear how these utilities were derived. Future benefits were discounted at 3%.
Direct costs The authors reported that they had taken account of intervention costs, which included diagnosis, drugs and monitoring of treatment, and had deducted costs from future savings from a reduction in the number of hip fractures. The model also included costs in added life years. The resource quantities appear to have been assumed by the authors and synthesised using modelling. The price year and the source of cost data were not provided. Future costs were discounted at 3%.
Statistical analysis of costs Indirect Costs Indirect costs were not included in the analysis.
Currency Swedish kroner (SEK) were converted to US dollars ($) using an exchange rate of 1$ = SEK 8.0.
Sensitivity analysis A sensitivity analysis was central to this paper. The parameter of particular interest was the duration of treatment effect after discontinuation. The inclusion of costs in added years of life and age at onset of treatment were also explored. All sensitivity analyses were one-way.
Estimated benefits used in the economic analysis Results were presented separately for the population with a baseline hip fracture relative risk of unity and the population with a two-fold increase in baseline hip fracture risk. Treating one woman for 5 years with treatment starting at age 50 years and with a baseline relative risk of hip fracture of one with a duration of effect of 5 years, resulted in 0.004 QALYs gained. Treatment onset at 60 years under the same assumptions resulted in 0.010 QALYs gained. For the population with two-fold increase in baseline risk the interventions would result in 0.007 QALYs gained for treatment onset at age 50 and 0.019 QALYs gained for treatment onset at age 60.
Cost results The authors assumed that total treatment costs for the first intervention would be $625 per year, reflecting the costs of bisphosphonate therapy. The cost of the second intervention was assumed to be $250, resembling the costs of HRT therapy. The cost of an extra year of life for individuals aged over 65 was assumed to be $19,900, and $4,600 for individuals aged under 65.
Synthesis of costs and benefits Costs and benefits were combined in average cost per QALY ratios resulting from comparisons of treatment with no treatment. The two treatments were reported separately under the baseline assumption that treatment effect wore off after five years. Cost per QALY gained decreased from $745,000 at treatment onset at age 50 to $17,000 at treatment onset at age 80 with an intervention costing $625 per year (e.g. bisphosphonates) and baseline relative risk of unity. With the same intervention, cost per QALY decreased from $370,000 at treatment onset at age 50 to being cost-saving at treatment onset at age 80 assuming two-fold increase in baseline hip fracture risk. Similarly, cost per QALY decreased from $269,000 to $72,000 for an intervention costing $250 per year (HRT) between treatment onset at age 50 to 60 years. Assuming two-fold increase in baseline hip fracture risk, the cost per QALY decreased from $118,000 at treatment onset at age 50, to $20,000 at treatment onset at age 60.
The authors evaluated the sensitivity of the assumption that treatment effect lasted five years after treatment was discontinued. Cost-effectiveness estimates decreased as expected with increasing duration of effect. For example, costs rose more than 50-fold when the duration was assumed to change from indefinite to immediate. The effect of duration on cost-effectiveness was exponential. The inclusion of costs in added years of life increased the cost/QALY gained.
Authors' conclusions The authors concluded that cost-effectiveness is poor in patients under 70 years of age, and that cost-effectiveness estimates are very sensitive to the assumption about treatment effect duration.
CRD COMMENTARY - Selection of comparators Fundamentally, this study did not compare real treatment alternatives, but hypothetical treatment scenarios for which attributes of treatments were assumed. The study made two comparisons, one of a bisphosphonate-like intervention compared to no treatment, and one of HRT-like treatment compared to no treatment, under different sets of assumptions. It may have been more relevant to have presented an incremental analysis of the two treatment strategies.
Validity of estimate of measure of effectiveness The estimate of effectiveness was based on the authors' assumptions without comprehensive support from relevant literature. For the purpose of illustrating hypothetical treatment scenarios this may have been a relevant estimate of treatment effect. However, a literature review of representative literature to arrive at possibly more realistic estimates would have strengthened the study.
Validity of estimate of measure of benefit The utilities ascribed to health states by age were explicitly reported by the authors. They did not, however, report the origin of these estimates, so it is difficult to assess their validity.
Validity of estimate of costs As with effectiveness, costs were also largely based on assumptions, and the lack of disaggregated reporting of resource use and unit prices makes it difficult to assess the validity of these estimates, or to generalise to other settings, even though a sensitivity analysis was conducted.
Other issues The authors discussed the issue of the transferability of the results of this study, and acknowledged the fact that the baseline risk estimates were taken from a Swedish population that may not be representative of other populations of women. The authors stated that hip fracture risk varies substantially within Europe, and that Sweden is a country with one of the higher absolute risk rates of hip fracture.
Implications of the study The authors commented that there is a need to target specific high-risk groups. Estimates of cost-effectiveness are also sensitive to assumptions about treatment effect duration, and the authors called for clinical studies to investigate this.
Source of funding Support from Lilly Research Centre
Bibliographic details Jonsson B, Kanis J, Dawson A, Oden A, Johnell O. Effect and offset of effect of treatments for hip fracture on health outcomes. Osteoporosis International 1999; 10(3): 193-199 Indexing Status Subject indexing assigned by NLM MeSH Age Factors; Aged; Aged, 80 and over; Computer Simulation; Cost-Benefit Analysis; Female; Hip Fractures /economics /prevention & Humans; Markov Chains; Middle Aged; Osteoporosis /economics /therapy; Quality-Adjusted Life Years; Treatment Outcome; control AccessionNumber 21999001933 Date bibliographic record published 31/03/2002 Date abstract record published 31/03/2002 |
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