If we knew in advance which patients had serious problems, solutions would be relatively easy. But often we don’t know. As a result, there is considerable debate over how many people should be tested and how frequently. One thing we do know, however, is that some people who should realize they have a problem fail either to see a physician or to receive the necessary preventive care.

The problem is especially acute in low-income areas, where there are sometimes epidemics of diseases many thought had been irradicated only a few years ago. Some inner cities now report skyrocketing rates of tuberculosis, hepatitis A, syphilis, gonorrhea, measles, mumps, whooping cough, etc. All too often, those who are infected see physicians too late. For example, at Harlem Hospital in New York City, only 30 percent of the women diagnosed with breast cancer live as long as five years, compared with 70 percent of white women and 60 percent of black women in the country as a whole.

Such statistics have led many to conclude that America’s private health care system is not serving low-income people and that a public system is needed. This view overlooks the fact that many of the people who are apparently not receiving needed preventive care are already part of a free public system, partly supported by funds collected from low-income, minority taxpayers. New York City, for example, recently experienced an epidemic of congenital syphilis (with about half the cases in the country), a surprising increase in cases of measles, and increasing instances of other preventable diseases. Yet, the city has perhaps the most extensive system of free health care and free public hospitals in the country.

In addition to low-income families (that presumably face financial constraints), many nonpoor families that can afford to purchase preventive care choose not to do so. One reason may be that diagnostic tests themselves expose patients to risks. According to one study, from 5,000 to 10,000 cases of breast cancer each year may be caused by x-rays. Health insurance companies, which clearly have a direct financial interest in such questions, generally do not require or encourage preventive medical tests. But the perspective of insurers may not be the best guide. Since people frequently switch carriers, insurers have less financial interest in the long-run consequences of a failure to detect a medical problem. And paying for diagnostic tests through insurers often doubles the cost of the tests.

Moreover, carefully conducted economic studies do not confirm that preventive medicine pays for itself. With the exception of targeted high-risk groups, preventive medicine generally adds to the cost of health. It is an investment in future good health, not a cost-control device. Further, attitudes toward risk vary. Risk-averse people place a higher value on preventive medicine than do those who are less risk-averse. Yet, in the current health care system, the delivery of preventive medical services tends to be determined by bureaucratic reimbursement policies rather than patients’ preferences.

Some propose to force private insurers to cover diagnostic tests (with no out-of-pocket cost to the patient), change Medicare rules to achieve the same objective for elderly patients, and make diagnostic tests free to targeted groups through a limited national health insurance program. Each of these proposals would use health insurance as a vehicle for the prepayment of the consumption of medical services. They would probably double the cost of the services (because of the administrative costs of third-party insurance). And they would give all decisionmaking power to third-party payers. Interestingly, countries that make all health care free to patients at the point of consumption do not necessarily expand the scope of preventive medicine. In the United States, we already perform more diagnostic tests than do most countries with national health insurance.

An ideal health care system would recognize that the question of whether a test is worth its cost depends as much on patient preferences and attitudes toward risk as on cost-benefit calculations. In the ideal system, patients would be the principal buyers of health care, and test manufacturers would market directly to them, as well as to health care providers. Health insurance would not be used as wasteful prepayment for the consumption of medical care. Instead, public policy would encourage private savings for diagnostic tests.