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Cost-effectiveness analysis of screening for osteoporosis in postmenopausal Japanese women |
Nagata-Kobayashi S, Shimbo T, Fukui T |
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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 Four main strategies to determine the cost-effectiveness (CE) of screening for osteoporosis in Japanese women were compared. Dual energy X-ray absorptiometry (DXA) of the femoral neck was selected as the screening method. The following strategies were compared:
no intervention,
hormone replacement therapy (HRT) for patients with a diagnosis of osteoporosis,
HRT for patients with both osteopenia and osteoporosis after screening, and
universal HRT without screening.
Additional analyses evaluating alendronate, and the effect of following Japanese guidelines on osteoporosis definition, were also performed.
Study population The hypothetical population comprised a cohort of asymptomatic, 50-year-old postmenopausal Japanese women with an average risk of breast cancer.
Setting The setting was the community. The economic study was carried out in Japan.
Dates to which data relate The effectiveness evidence was obtained from studies dating from 1992 to 2000. For the cost data, the date range was 1996 to 2000. The price year was 2000.
Source of effectiveness data The evidence was derived from a review or synthesis of completed studies and estimates based on authors' opinions.
Modelling A computer-simulation state-transition Markov model was used to estimate the cost and effectiveness of preventive strategies during a time horizon of 30 years. In each annual cycle of the Markov model, each person in the cohort was assumed to transit among health states. The health states considered were complete health, acute hip fracture (HF), able to walk outside after an HF (good prognosis), unable to walk outside after an HF (poor prognosis), and death.
Outcomes assessed in the review The following parameters were estimated in the model:
the proportion of women screened in each risk group, (according to BMD classification by DXA);
the incidence and case-fatality rate of HF;
mortality other than for HF;
prognostic probabilities after HF;
the relative risk of HF; and
the effectiveness of HRT in reducing the incidence of HF.
Study designs and other criteria for inclusion in the review Articles in Japanese and government publications were sought. Studies on secondary osteoporosis were excluded. The types of study designs used were epidemiological, population-based and observational studies, meta-analyses and other published literature.
Sources searched to identify primary studies MEDLINE was searched from 1985 to November 2001.
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 Ten studies provided the effectiveness evidence.
Methods of combining primary studies A narrative method was used to combine studies.
Investigation of differences between primary studies Results of the review The proportion of women screened (according to BMD classification by DXA) was 41.7% for low risk of HF, 31.0% for osteopenia and 27.3% for osteoporosis.
The incidence of HF (per 10,000 person-year) ranged from 2.39 in the 50- to 59-year age group to 147 in the 80- to 89-year age group.
The case-fatality rate for HF was 0.11,
The probability of a good prognosis after HF was 67%, and that of a poor prognosis after HF was 22%.
The relative risk of HF was 1 in the low risk of HF group, 2.6 in patients with osteopenia and 6.5 in patients with osteoporosis.
The relative incidence of HF with HRT was 0.75.
The authors gave ranges for most of the parameters included in the model.
Methods used to derive estimates of effectiveness This analysis was based on published data and authors' assumptions.
Estimates of effectiveness and key assumptions Hip fracture was considered the only outcome of preventive treatment because of its profound effect, both on the patients' survival and their quality of life. The authors assumed that only one of three possible outcomes (good prognosis, poor prognosis or death) ensued after HF occurred.
Measure of benefits used in the economic analysis The measure of benefit used was the quality-adjusted life-years (QALYs). The utility data were derived from a published study in which utility was measured by the time trade-off method in 194 women older than 75 years who were at high risk of HF (see Other Publications of Related Interest). In the base-case analysis, utilities were defined for the five health states. The utilities were 1.0 for a completely healthy state, 0.31 for acute HF and for good prognosis after HF, 0.05 for poor prognosis after HF, and 0 for death. The ranges for state utilities were also taken from the aforementioned study.
Direct costs The authors used medical charges based on a reimbursement schedule as a substitute for medical costs because a cost-to-charge ratio was not determined in Japan. The direct medical costs included were the screening cost of measuring BMD by DXA, the treatment cost of HRT, the treatment cost for acute HF, and the follow-up cost for patients after HF. With the exception of drug costs, all the costs were derived from published literature. The authors reported that they did not include the cost of other treatments for osteoporosis, such as dietary therapy and physical exercise.
All the medical costs were calculated in yen for the year 2000, or were revalued to prices in 2000 according to the medical component of the consumer price index. Discounting was performed at a rate of 3%. The quantities and the total costs were derived using modelling. The resource quantities and the costs were not reported separately.
Statistical analysis of costs No statistical analysis of the quantities or costs was reported.
Indirect Costs Although the authors stated that the perspective was societal, no indirect costs were included in the study.
Currency Japanese yen (Y). The conversion rate in 2000 was Y110 = 1 US dollar ($).
Sensitivity analysis Sensitivity analyses were performed to assess the robustness of the results. The parameters evaluated were:
the proportion of women screened in each risk group;
the incidence of HF;
the case-fatality rate of HF;
prognostic probabilities after HF;
the relative risk of HF;
the drug effect of HRT in reducing the incidence of HF;
patient compliance in initiating HRT;
medical costs;
utility;
discount rate; and
impact of the time horizon on the results.
Two additional analyses were performed. The first considered alendronate as an effective drug for osteoporosis. The second considered the clinical practice guidelines developed by the Japanese Society for Bone and Mineral Research, whose definition of osteoporosis is different from that used in the study.
The ranges for the sensitivity analyses were reported. With the exception of compliance, which was assumed to range from 50 to 100%, the ranges were taken from published sources. However, the method used to select the ranges and the types of analyses used were not described.
Estimated benefits used in the economic analysis The effectiveness results for the four strategies were:
for strategy 1 (no intervention), 19.0087 QALYs;
for strategy 2 (HRT for patients with osteoporosis determined by screening), 19.0288 QALYs;
for strategy 3 (HRT for patients with osteopenia or osteoporosis determining by screening), 19.0383 QALYs; and
for strategy 4 (HRT for all members of the cohort without screening), 19.0433 QALYs.
The marginal effectiveness was calculated as the effectiveness of a strategy minus the effectiveness of the next most effectiveness strategy. The marginal effectiveness due to preventive treatment was 0.0201 QALYs for strategy 2 compared with strategy 1, 0.0095 QALYs for strategy 3, and 0.0050 QALYs for strategy 4.
Cost results The total costs were Y214,000 for strategy 1, Y322,000 for strategy 2, Y462,000 for strategy 3 and Y659,000 for strategy 4.
The marginal cost was calculated as the cost of a strategy minus the cost of the next most costly strategy. The marginal cost for the prevention of osteoporosis in a 30-year model in the base-case analysis, with a 3% discount rate, was Y108,000 for strategy 2 compared with strategy 1, Y140,000 for strategy 3, and Y197,000 for strategy 4.
Synthesis of costs and benefits The marginal cost-effectiveness for each strategy above the next most effective strategy in the base-case analysis was Y5.36 million/QALY for strategy 2 compared with strategy 1, Y14.7 million/QALY for strategy 3, and Y39.4 million/QALY for strategy 4.
In the sensitivity analysis, drug effects and the treatment costs of HRT had a large influence upon the marginal cost-effectiveness. When the relative risk of HF under HRT was set at 0.5, or the treatment cost of HRT was decreased to Y13,000/year (50% of the base-case value), the marginal cost-effectiveness was reduced by about 60%.
The discount rate also had a small but significant effect on the results. When the discount rate was set at 0.05, the marginal cost-effectiveness increased by about 30%.
When the time horizon was prolonged from 30 to 40 years, the marginal cost-effectiveness was Y2.18 million/QALY.
Neither the degree of patient compliance with HRT, nor the other parameters evaluated, had a significant effect on the results in the sensitivity analysis.
When alendronate was used as the preventive pharmacotherapy, the marginal cost-effectiveness of a strategy compared with the next most effective was Y9.96 million for strategy 2 compared with strategy 1, Y26.8 million for strategy 3, and Y71.5 million for strategy 4.
Applying Japanese guideline criteria, the marginal cost-effectiveness compared with no intervention was Y5.40 million for strategy 2, Y8.69 million for strategy 3, and Y41.7 million for strategy 4.
Authors' conclusions The main result of this study was that the only strategy that appears to have been cost-effective was to screen women and treat only those with a diagnosis of osteoporosis with hormone replacement therapy (HRT). All the other strategies were not cost-effective. The treatment cost of HRT made a large difference between the strategies, while none of the other costs contributed to the differences observed. The current study suggested that screening postmenopausal Japanese women and providing preventive treatment to those with osteoporosis might be an acceptable strategy, but its cost-effectiveness seems only "fair".
CRD COMMENTARY - Selection of comparators A justification was given for the comparators used. The authors considered DXA of the femoral neck as the screening method because of its safety in BMD measurement and the established predictability of HF. They selected HRT as the preventive treatment for osteoporosis because its benefits have been demonstrated in many studies. The authors also evaluated different alternatives (alendronate, Japanese guidelines criteria) in the sensitivity analysis. The authors explicitly excluded primary prevention, such as physical exercise and calcium intake. You should decide if these represent widely used technologies in your own setting
Validity of estimate of measure of effectiveness The authors did not state that they performed a systematic review of and the epidemiological parameters were selectively taken from the literature. The authors appear to have used the data from the available studies selectively. They did not consider the impact of differences between the identified studies when estimating the effectiveness.
The authors derived estimates of effectiveness from published literature and authors' assumptions. However, they did not provide any justification for their choice of assumptions. The estimates were investigated in a sensitivity analysis, although no justification for the ranges selected was given.
Validity of estimate of measure of benefit The authors used the QALYs, derived from published literature, as a measure of benefits. The methods used in the literature were reported and the preferences were based on a comparable population. Sensitivity analyses on the utilities and time horizon were conducted. The ranges were reported, but not their selection criteria.
Validity of estimate of costs Although the authors reported that the study had been conducted from a societal perspective, the indirect costs were not included. Their influence in the results could be significant, even though the proportion of working women in this age group was probably small.
The costs and the quantities were not reported separately and this would make it difficult to rework the analysis for other settings. The authors acknowledged the difference between medical charges and medical costs, but they used medical charges for the study based on a reimbursement schedule as a substitute. Sensitivity analyses of the medical costs were conducted to assess the robustness of the estimates used. Discounting was appropriately carried out since the time horizon of the model was 30 years. A revaluation of the costs was carried out and the price year was reported. This will aid any future reflation exercise.
Other issues The authors compared their findings with those from other studies which, in general, showed that their findings were concordant. The authors did not address the issue of generalisability of the results to other settings. The authors' conclusions reflected the scope of the analysis but, because they selected young women and there were insufficient data for women over 80 years of age, the extrapolated probabilities and utilities for a 40-year time horizon analysis might be somewhat unstable.
The authors acknowledged some limitations of their study. First, the exclusion of other types of fractures. Second, the use of some foreign data to populate the model, such as the relative risk of fractures and HRT effectiveness.
Implications of the study When compared with the cost-effectiveness of other screening programmes in Japan, the current result for osteoporosis is relatively high. However, since these programmes have been accepted and conducted across the country for a considerable time, the marginal cost-effectiveness of screening for osteoporosis seems only fair. The authors pointed out that primary epidemiological data for probabilities and utilities among older women are needed. Other than drug therapy, the prevention of falls, or the use of hip protectors is likely to reduce the incidence of hip fractures and improve the patients' quality of life. The authors stated that further studies around these issues might elucidate more effective programmes at the community, as well as the individual level.
Bibliographic details Nagata-Kobayashi S, Shimbo T, Fukui T. Cost-effectiveness analysis of screening for osteoporosis in postmenopausal Japanese women. Journal of Bone and Mineral Metabolism 2002; 20(6): 350-357 Other publications of related interest Salkeld G, Cameron ID, Cumming RG, Easter S, Seymour J, Kurrie SE, et al. Quality of life related to fear of falling and hip fracture in older women: a time trade off study. BMJ 2000;320:341-6.
Indexing Status Subject indexing assigned by NLM MeSH Absorptiometry, Photon; Aged; Aged, 80 and over; Bone Density; Cost-Benefit Analysis; Female; Fractures, Bone /complications /prevention & Hormone Replacement Therapy; Humans; Incidence; Japan /epidemiology; Mass Screening /economics; Middle Aged; Osteoporosis, Postmenopausal /complications /diagnosis /economics /epidemiology; Practice Guidelines as Topic; Prognosis; Risk Assessment; Sensitivity and Specificity; control AccessionNumber 22003006563 Date bibliographic record published 31/12/2004 Date abstract record published 31/12/2004 |
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