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What's Behind The Screens?
The major and most expensive part of medical technology as applied today appears to be far more for the satisfaction of the health professions than for the benefit of the consumers of health care.
Dr Halfdan Mahler, Director General, the World Health Organisation, 1984.
Screening for disease is the latest medical fad. The argument is that prevention is better than cure; that screening for heart disease and cancers (principally) will prevent those diseases.
But screening for disease is not prevention, it is merely early detection. If a cancer, for example, is detected, that means it is there and hasn't been prevented.
This technique is not without risk. There is little point, for example, in the early detection of a disease for which there is no cure. This merely worries the patient unnecessarily. There are also the considerable problems associated with both false positive and false negative results. People told they may have cancer have been devastated — even negative results have resulted in depression and withdrawal from society.
This paper looks at the experience of screening for breast and cervical cancers, and coronary heart disease; at the accuracy (or lack of it) of screening machines and human operatives. We also consider evidence that suggests that little is to be gained by patients from such procedures.
The fallacies. We constantly hear from those who would change our lives that, if we did change, thousands of lives would be saved. This is the fallacy of cheating death. We are not an immortal species. No matter what we do we cannot expect to live for ever.
In the Western world, life-expectancy is approaching its biological maximum. Whatever we do, very little is likely to be achieved in terms of increased life-expectancy.
There are other fallacies: the fallacy that an association is causal. Post hoc ergo propter hoc — I was ill now I'm cured, therefore my treatment cured me — is not necessarily true. Just because one thing follows another does not mean necessarily that one caused the other. Is day caused by night? — or vice versa?
There's the ecological fallacy which transfers to individuals relationships which appear in populations.
And the surrogate fallacy. Cancer screening has been hailed as a great success. But what they are measuring is the number of women being screened. This is a surrogate for what should be the real end point of cancer screening — the reduction of cancer deaths. These are increasing. Some success!
Also considered are the cost-effectiveness of screening and the other uses to which the findings of screening programmes are put: decisions about levels of hospital services throughout the country.
In many cases, all that screening and subsequent interventions have achieved is to transfer the cause of death from one category to another, an achievement which has no importance unless, perhaps, it is accompanied by the prolongation of useful and happy life.
And let us not forget that prolongation of death is not the same as prolongation of life.
Click here for a detailed paper on screening complete with references
Last updated 13 December 2000
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