Developing better economic models of osteoporosis: considerations for the calculation of the relative risk of fracture.
OBJECTIVE
Simulation models are often used to assess cost-effectiveness of osteoporosis therapies. Many cost-effectiveness analyses are interested in a subset of the general population, such as high-risk patients. As the analyses are very sensitive to the assumed risk of fracture, it is imperative that the rates accurately reflect the fracture risk in the specified target population. The objective of this study was to describe the methodological difficulties and present some possible solutions for calculating the risk of fracture in target populations of interest.


METHODS
For binary risk factors, a method for converting from a relative risk (RR) for people with a risk factor relative to those without, to an RR in the target population compared with the general population, is described. For continuous risk factors (i.e., bone mineral density [BMD]), data are often provided as an RR of fracture per SD decrease. A method for converting from an RR per SD decrease to an RR in those below a certain BMD threshold, compared with the general population, is presented.


RESULTS
These results should allow future economic models to more accurately incorporate existing knowledge of risk factors by introducing methods to calculate fracture risk estimates in a target population.


CONCLUSIONS
It illustrates the importance of considering the prevalence of risk factors in the general population when calculating RR in a target population.
Black
Dennis M
DM
UCSF Prevention Sciences Group, University of California-San Francisco, San Francisco, CA, USA.
Palermo
Lisa
L
Grima
Daniel T
DT
D000368:Aged; D015519:Bone Density; D003198:Computer Simulation; D003362:Cost-Benefit Analysis; D005260:Female; D050723:Fractures, Bone / Q000191:economics* / Q000209:etiology; D005598:Fractures, Spontaneous / Q000191:economics / Q000209:etiology; D006801:Humans; D017059:Models, Econometric; D016011:Normal Distribution; D010024:Osteoporosis / Q000150:complications / Q000191:economics*; D015663:Osteoporosis, Postmenopausal / Q000150:complications / Q000191:economics; D016016:Proportional Hazards Models; D012306:Risk; D018570:Risk Assessment / Q000191:economics* / Q000379:methods; D012307:Risk Factors