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Which screening strategy using BMD measurements would be most cost effective for hip fracture prevention in elderly women? A decision analysis based on a Markov model |
Schott A M, Ganne C, Hans D, Monnier G, Gauchoux R, Krieg M A, Delmas P D, Meunier P J, Colin C |
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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 compared two screening strategies based on the measurement of bone mineral density (BMD), measuring the BMD of all women (screen all strategy) versus measuring the BMD only for those who have at least one risk factor. The risk factors were:
a history of fracture after the age of 50 years,
menopause before 40 years of age,
a history of maternal hip fracture,
a body mass index lower than 19 kg/m2, and
the use of corticosteroids (>7 mg a day equivalent prednisone) for more than 3 months.
No screening was used at the base-case. Screening was carried out using dual-energy X-ray absorptiometry (DXA).
Economic study type Cost-effectiveness analysis.
Study population The study population comprised postmenopausal, 70 year-old women with no history of hip fracture.
Setting The setting was outpatient care. The economic study was carried out in France.
Dates to which data relate The effectiveness data was obtained from sources published between 1989 and 2004. The cost data came from sources published between 1989 and 2003.
Source of effectiveness data A review of the literature was used to inform probabilities within the decision tree analysis and transition probabilities within the Markov model. Specifically, the model incorporated data on:
the treatment effect (reduction in hip fracture incidence);
the annual probabilities of institutionalisation and institutionalisation after hip fracture;
the annual probabilities of death from any cause and death after a hip fracture;
the annual probability of sustaining a hip fracture in institutionalised women;
the relative risk of death in an institution versus the general population;
the sensitivity and specificity of DXA (with threshold of BMD t score <= -2.5) if risk factor used to predict hip fracture; and
the sensitivity and specificity of DXA (with threshold of BMD t score <= -2.5 if no risk factor used to predict hip fracture (screen all strategy).
Modelling The authors used a decision tree analysis and Markov modelling to depict the disease states of "good health", "suffer a hip fracture", "die" and "be admitted to a nursing home for other reasons". During each cycle of 1 year, the individual might move from one health state to another or suffer none of the events and remain in the same Markov state. Death was defined as an absorbing state. The model was run for a period of 10 years. It was validated by assuming that treatment conferred no reduction in fracture probability, and by confirming equal probability of hip fracture across all treatment strategies.
Sources searched to identify primary studies Baseline probabilities were estimated from French national registers when available and, where not available, scientific papers were used. The authors reported that most data were derived from European prospective cohort studies with older women comprising the patient sample.
Methods used to judge relevance and validity, and for extracting data The authors did not report that any systematic strategy was used to search for relevant literature. Instead, they seem to have selected sources that provided data relevant to the decision model. There were no identified inclusion or exclusion criteria for data sources, and no discussion of how some data sources were combined to obtain the specific parameter value used in the analysis.
Measure of benefits used in the economic analysis The summary measure of health benefit was the number of years without a hip fracture over the 10-year period.
Direct costs The costing was carried out from the perspective of the health care system perspective. It incorporated the costs of BMD testing, preventive treatments for women with low BMD, hospitalisation and rehabilitation of patients with a hip fracture, institutionalisation and the screening campaign. The authors explicitly stated that non-medical direct costs were not included in the analysis. The unit costs were based on average costs observed in practices, costs from a French screening campaign, and French hospitalisation data. The costs were discounted at a rate of 5% to account for time preferences.
Statistical analysis of costs The authors treated the costs deterministically.
Indirect Costs Indirect costs were not relevant to the perspective adopted and were appropriately not included in the analysis.
Sensitivity analysis The authors noted that they used a one-way sensitivity analysis to explore the effect of variability in the parameter values. A two-way analysis was then used to further explore parameters that strongly influenced the results.
Estimated benefits used in the economic analysis Screening all women resulted in 8.27 years without hip fracture over 10 years.
Screening women at risk resulted in 8.03 years without hip fracture over 10 years.
No screening resulted in 7.84 years without hip fracture over 10 years.
Cost results Screening all women cost EUR 48,600.
Screening women at risk cost EUR 48,400.
No screening cost EUR 46,800.
Synthesis of costs and benefits Compared with no screening, the incremental cost-effectiveness ratio was EUR 8,290 for screening women at risk and EUR 4,235 for screening all women.
Screening women at risk was not preferred due to extended dominance (i.e. some combination of no screening and screening all women would provide greater outcomes at a lower cost).
The results were most sensitive to the number of cycles in the model, the cost of a nursing home, the probability of having a BMD below 2.5, the cost of treatment and the cost of DXA. Despite this, the authors reported that the "hierarchy of cost-effective strategies was not altered, the strategy 'screen all' was persistently the more cost effective".
Authors' conclusions "Screen all" appear to have been the most cost-effective strategy.
CRD COMMENTARY - Selection of comparators The authors compared three screening strategies (I.e. no screening, screen all and screen those at risk). These three alternatives covered all the options available, although readers should consider the criteria used to define 'at risk' and assess whether these are applicable to their own setting.
Validity of estimate of measure of effectiveness The authors' review of the literature could have been better described to enable the reader to understand the extent to which a systematic review was undertaken or literature was chosen selectively to provide data relevant for inclusion in the model. In addition, where primary data were combined, the authors could have described how they arrived at the single parameter value, or how the literature was used to define limits in the sensitivity analysis. The report concerning the gathering of data inputs would have been improved by a more detailed and accurate reporting of the methodology involved. Validity of estimate of measure of benefit The authors used the number of years without a hip fracture as their primary measure of health benefit. This is an appropriate measure and can be compared with other studies exploring primary and secondary hip replacements. A preference base measure, such as quality-adjusted life-years, would have enabled greater comparability of the results. In addition, given that the authors cited a comparable cost-utility study, it was unclear why they did not incorporate patient preferences.
Validity of estimate of costs The costing was carried out from the perspective of the health care system. The costs relevant to this perspective were reported to have been included. The authors appropriately discounted the costs. A useful breakdown of the unit costs, which enables readers to assess the applicability of the costing analysis to an alternative setting, was provided.
Other issues The authors made comparisons with other relevant literature, although they noted the lack of cost-effectiveness results comparing screening strategies. Despite this, they noted one study that conducted a cost-utility analysis and reported comparable results. The issue of generalisability to other settings was explicitly discussed. The authors recommended further work with locally appropriate risk factors, or more comprehensive combinations of risk factors, to improve the broader generalisability of the results. The results were comprehensively reported and were clear to interpret. The conclusions accurately reflected the scope of the study and the results presented. Limitations in terms of the modelling assumptions were noted.
Implications of the study The authors did not make specific recommendations for policy or practice following on from their study. They noted instead that much information, including the frequency of screening and the optimal age of screening, is still lacking. Further work is recommended (as noted above).
Bibliographic details Schott A M, Ganne C, Hans D, Monnier G, Gauchoux R, Krieg M A, Delmas P D, Meunier P J, Colin C. Which screening strategy using BMD measurements would be most cost effective for hip fracture prevention in elderly women? A decision analysis based on a Markov model. Osteoporosis International 2007; 18(2): 143-151 Indexing Status Subject indexing assigned by NLM MeSH Absorptiometry, Photon /economics /methods; Aged; Aged, 80 and over; Bone Density /physiology; Cost-Benefit Analysis /economics; Decision Trees; Female; Hip Fractures /economics /prevention & Humans; Markov Chains; Monitoring, Physiologic /economics /methods; Postmenopause /physiology; Risk Factors; control AccessionNumber 22007000259 Date bibliographic record published 31/08/2007 Date abstract record published 31/08/2007 |
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