The United States along with many other rich countries encourages widespread so-called preventive screening for various diseases, including breast, prostate, and other cancers, cardiovascular disease, diabetes, kidney functioning, and many other serious, and even not so serious, diseases. It is often claimed that prevention of diseases should be given the highest priority in order to early detect treatable serious medical problems. But these gains have to be balanced against the considerable cost of extensive preventive screening. The US and other nations are very likely over-screening for various medical problems.
The benefits of screening depend on the seriousness of the disease, and the gain from early detection. The latter in turn depend crucially on the treatment success when a disease is detected early compared to when it is detected at a later stage. For example, treatments for both prostate and breast cancers seem to be more effective when these diseases are detected early, although that is disputed by reputable researchers and physicians. However, it is clear that early detection of Alzheimer’s’ disease has little advantage since there are no effective treatments for this highly debilitating disease. Early detection of this disease may have other advantages if that enables individuals to plan for their increasing mental feebleness, such as preparing or modifying wills, and takng other decisions that require some mental acuity. On the other hand, it may reduce quality of life by causing great fear of the impending disease.
Along with the benefits often come major costs of widespread screening, costs that frequently outweigh the advantages. For example, if only a very small fraction of the population were likely to have a disease, perhaps one chance in 500 or less, it may not make much sense to screen everyone. Take, for example, Huntington’s disease, which affects a very small fraction of the population. With such a low general risk of having the genes that cause this disease, it is much more cost efficient to screen only individuals with a much higher probability of having the disease. These are persons who have family members with Huntington’s. Even then, studies show that many potential carriers of the deadly genes prefer not to be tested since no treatments are available, and they fear living with the news that they will eventually get this disease.
More generally, worry about test results is sometimes a sizable cost of widespread screening. This is partly because many medical tests frequently give false positives that may lead to unnecessary, worrisome, and sometimes risky additional tests and treatments before it is determined that nothing is really wrong. The widely used PSA test to screen for prostate cancer is a good example. Elevated or rapidly rising PSA levels are often indications of tumor in the prostate. However, many individuals have relatively high PSA levels without any tumor presence, sometimes because they have enlarged prostates. Others have rising PSA levels also for other reasons. Annual PSA tests may be indicated for men over age 45 or so with family histories of prostate cancer, but they are less frequently needed for men who have little prostate cancer in their family.
Many tests sometimes lead to serious complications, and any complications should be balanced against the gains from early detection of medical problems. Every blood test carries some risk of infection and contamination. X-rays, MRIs, CT scans, ultrasounds and the like have radiation and other risks. Probing for tumors with biopsies, colonoscopies, and other invasive tests carry a variety of risks.
The benefit-cost evaluation of any suggested widespread screening would depend on the net effect of the factors I discussed. First of all, benefits depend on the size of the gain in treatment from early detection of a disease or other medical problems. This gain has to be adjusted for the probability of finding a serious problem since the lower that probability, the less the expected gain from extensive screening. Costs start with the cost of the methods used to screen, including the value of the time and inconvenience of individuals being screened. The likelihood of various side effects from these methods also must be weighed. The fear engendered by false positives can be important, although that has to be balanced against the peace of mind that comes from getting (true) negative results.
Preventive care is often considered the gold standard of good medical practice. It is easy to get both doctors and patients to agree when either the government (i.e., taxpayers) or insurance companies (i.e., others who are insured) pay the vast majority of the costs. A rethinking of this standard is warranted, and such a rethinking would be encouraged if individuals paid a much larger fraction of their out of pocket medical expenses.