A critical structured review of economic evaluations of interventions for the prevention and treatment of osteoporosis

Osteoporosis is a major cause of morbidity, mortality and resource cost amongst the elderly population. Hip fracture is the most serious of the osteoporotic fractures, with approximately 10-20% of patients dying within six months of sustaining a fracture. Furthermore, hip fractures are the most expensive manifestation of osteoporosis, incurring about 87% of the total costs of osteoporotic fractures. This public health and economic burden is likely to increase in developed nations due, in part, to ageing populations. In addition, there is strong evidence that the age-specific incidence of fracture is rising. There are a number of treatments which can be used to prevent fracture including hormone replacement therapy (HRT), bisphosphonates, vitamin D and calcium. These interventions have been used for primary prevention, secondary prevention and the treatment of established osteoporosis. This Discussion Paper details the results of a structured review, the purpose of which was to identify and critically appraise economic evaluations relating to interventions for osteoporosis. The focus of the work is a critical assessment of the methodology of those studies. A total of 16 economic evaluations was identified on the basis of a computerised search of three bibliographic databases. All studies were based on decision analytical models and all took the form of cost-effectiveness analysis. Seven studies were from the US and four from the UK. The majority of studies focused on either primary prevention alone (seven) or both primary and secondary prevention where high-risk women were identified on the basis of bone mineral density screening (seven). Most studies considered the cost-effectiveness of HRT. Most of the published studies conclude that treatment using HRT is relatively cost-effective among symptomatic women or women who have had a prior hysterectomy. In contrast, for asymptomatic women, the results are more equivocal. The most recent cost-effectiveness analysis was undertaken by the National Osteoporosis Foundation (NOF) which makes the explicit assumption that HRT is the treatment of choice. For women unwilling or unable to take HRT, the next recommended treatment was alendronate; should alendronate not be tolerated, calcitonin was recommended. Many of the models included in the review exhibit methodological weaknesses which suggest heir results should be treated with some caution. One of these concerns the dearth of formally elicited health state preference data from patients or members of the public: only two studies in the review derive preferences empirically rather than use the authors’ judgement. A second limitation of many studies is the inappropriate application of costeffectiveness decision rules with the frequent use of average cost-effectiveness ratios. Areas of methodological controversy, such as whether or not to include costs unrelated to osteoporosis in life-years added as a result of treatment, increase uncertainty regarding how to interpret the results of the studies.