Treatment thresholds for preventive therapy: a simplified example of therapy for prevention of hip fractures

Physicians intuitively understand that preventive treatments may be worthwhile for patients at very high risk of a disease, but not for those with a very low risk. Somewhere in between lies a probability of the disease, called the "treatment threshold" above which prevention is worthwhile and below which it is not. This essay presents an approach to clinical decision-making based on methods developed for bedside decision analysis. Using a hypothetical example of a treatment to prevent hip fracture, this model demonstrates that the treatment threshold (the probability of fracture above which prevention is cost-effective) decreases as 1) the effectiveness of the treatment increases, 2) the cost of the drug decreases, 3) the cost of physician visits and tests to monitor treatment decreases, 4) the value placed on the fracture (medical costs, death, disability) increases. When sufficient data becomes available, estimates of treatment threshold can be combined with estimates of an individual's risk of fracture to aid clinical decision-making about prevention of fractures.