A book published recently and entitled <Overdiagnosed: Making People Sick in the Pursuit of Health> by three reputable physicians (H. Gilbert Welch, Lisa M. Schwartz, and Steve Woloshin), argues forcefully that the nation is spending too much money on preventive care. This is doubtless regarded as heresy in some circles: the orthodox view is that prevention is the key to economizing on the expenses of health care: "an ounce of prevention is worth a pound of cure." The recent health care reform act seeks to promote preventive care.
Preventive care does reduce health costs in some cases, but not in all, and maybe not in most. The costs of prevention have to be weighed along with the benefits. And private and social costs have to be distinguished. Subsidy programs such as Medicare reduce the private costs of medical treatment to patients, but the social costs are not reduced; their incidence is merely shifted. Generally, preventive care has two phases: screening and treatment.
So not only is there compelling evidence of what Welch and his coauthors call overdiagnosis; there are good reasons to believe the evidence because the incentive structure for screening and preventive care makes overdiagnosis a theoretical prediction as well as an empirical reality.
source：http://www.becker-posner-blog.com/2011/02/the-overdiagnosis-problemposner.html
