PREVENTIVE MEDECINE: SCREENING
Screening specific groups of people who are either totally without symptoms or who have symptoms that prompt a search for disease in its earliest stages has been a part of preventive medicine in the UK for about seventy years, since the regular examination of schoolchildren was first introduced on a national basis. Shortly afterwards-during World War I-pre-natal care for mothers and the medical examination of young babies were recommended and soon became commonplace. In 1943 mass X-ray screening for tuberculosis started nationally. The idea behind this was not only to find people with the disease and treat them but to remove them from contact with others, so limiting the spread of the disease. Today, the importance of infectious diseases has lessened and most screening programmes are on the lookout for degenerative or potentially chronic conditions. But why should people want to be screened for diseases they don’t have?
Perhaps the most widespread form of general health screening in the adult population is the insurance medical for a job, a mortgage or a life-insurance policy. Naturally the insurance company wants to try to reduce the odds in this gamble. Put simply, the policy-holder is betting the company that he or she will die and that it will have to pay up. The company, on the other hand, is betting that the policyholder will live-at least until all the premiums are paid. This kind of screening protects the insurance company and ensures that they win more ‘bets’ than they lose. It does nothing for the health of the individual.
The second reason for screening is to protect other people in the community. The control of infectious diseases and the health screening of people who work dangerous machinery are two good examples. Again the main intention is not to protect the individual screened.
In the USA, and to a lesser extent in other westernized countries, screening has become a fashionable alternative to personal health services. Millions of people every year go through a broad batch of screening tests and procedures instead of seeing a doctor. Abnormal results then ensure that they get to see a doctor. People in the US have been brought up to think of the ‘annual physical’ as an essential part of preventive health care but the mood of experts is changing on this. It is now thought that healthy young people (under 40) need only have a thorough medical check-up every five years-not yearly as was recommended in 1947 by the American Medical Association. The concept of even a five-yearly checkup from this age is alien to most British people. After the age of 40 more frequent checks are recommended in the US.
The fourth reason for screening someone is to obtain a ‘healthy’ baseline of data so that should anything go wrong with the person in the future better clinical judgments will be made. The best example of this kind of screening is an electrocardiogram on a middle-aged man.
The final reason for screening an apparently healthy population is to detect conditions that are not apparent and which the medical profession can hope to influence in a positive way. But screening large populations is very expensive and time-consuming, and has an effect on the people being screened, so it behoves us to ask some tough questions before deciding to spend vast amounts of money and other resources on what is at first sight unquestionably a ‘good thing’.
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