Faculty of Medicine, Edward Ford Building, University of Sydney, NSW 2006, Australia. E-mail: steve{at}medicine.usyd.edu.au
As a callow youth from the colonies, I arrived at the Lambeth offices of St Thomas's Hospital Medical School Department of Clinical Epidemiology on a gloomy April Fool's Day 1974, the very day the NHS transmogrified into one of its (subsequently several) new structures. In Lambeth I discovered what Walter Holland and his colleagues had been up to by way of public health research in recent years. Dedicated research staff of eminence and skill were beavering away on projects to do with respiratory health, the health of schoolchildren and screening. I met the screening research workers, saw the data, and even worked on some of it, if with no great consequence, although for a post-doc it was a superb data set with which to 'play' in company with people who, in those early days of information technology, were at the forefront of computational and statistical innovation.
The South-East London Screening Study (SELSS) started in 1967 and was a trial of multiphasic screening for diseases of middle-age.1 It began 2 years before the first man set his foot on the moon. Nine years after the initial screening 'no significant differences were found between the (screened and unscreened) groups in any of the outcome measures' which included hospital admissions, general practice consultations, certified sickness and mortality. Costs of screening were also calculated. Although the total cost of the study is not clear, it influenced policy at the time to avoid the expensive error of publicly supported multiphasic screening. Thus in the light of this study a policy for the use of public money for multiphasic screening would have needed to find justification in intangible or individual benefits not identified by it.
The SELSS was concerned with screening as used in the search for disease in people recruited for that search, rather than the pursuit of asymptomatic abnormalities in patients already consulting a doctor for another purpose. The latter has come to be accepted as case-finding. Since the SELSS was performed, remarkably few similar studies have been done. The results from these are similar to those from the SELSS. Yedidia conducted multiphasic testing in California cannery seasonal workers and found one or more abnormalities in about 40% of workers.2 The Värmland scheme which tested a whole adult population in the county of Värmland in Sweden found one or more abnormalities in 31% of participants. These patients were grouped into six priority categories according to their expected need of medical care.3 What became of them is not clear.
In a study of Kaiser Permanente Foundation Health Plan members in California, comparing the fate of subjects urged to have annual multiphasic health check-ups for 16 years with that of subjects not so urged, the screened group experienced a 30% reduction in deaths from pre-specified 'potentially postponable' causes, largely associated with lower death rates from colorectal cancer and hypertension. In the Kaiser Permanente study, cervical screening and sigmoidoscopic examination for those aged 40 were included.4 The two groups did not differ to a statistically significant degree in total mortality and the enthusiasm for screening decreased.4
The SELSS provokes four major topics for our reflection in an era where much that was pioneered by the study has become common practice. First, the study brilliantly demonstrated the applicability of randomized trials to answering questions of importance for health services that transcend the clinical setting. What medical practitioners generally accept as evidence can properly form but a part of all that must be considered in the formulation of health policy. Those of EBM persuasion lament the gap that exists between medical evidence and medical practice. However, a larger, more troubling space exists between the use that could be made of evidence in the health policies we construct and the use made of it in practice.
As part of this effort, the randomized trial has much to commend it. At a conference in Canberra, Australia, last year I argued that to address health inequality what we needed most urgently was evidence of interventions that successfully have reduced health inequalities. In fact, there are virtually none. Meanwhile, furrowed-brow conferences review the descriptive data that link the distribution of health according to economic status and social capital with little dependable evidence to guide the investment of the next dollar.
The second point the SELSS raises for consideration today is that, while accepting its results, it must be seen as a creature of the technology and practice of its time. The comprehensive first screening examination in 1967 included self-administered questionnaires, anthropometry, visual and auditory tests, lung function tests, ECG blood tests and tests for occult blood in the stool.5 We now have evidence of the modest benefit of cervical cytological screening, mammography and tests for colonic abnormalities related to bowel cancer.68 Not that this progress invalidates the SELSS. It simply means that, were multiphasic screening to be revisited now as a matter of public health policy, a new trial would be needed. Likewise, the management of screening and the conduct of the evaluative randomized controlled trials (RCT) would benefit from the capacity of information technology to amass and manage large amounts of data.
Third, much has been written about the importance of being able to offer the subject who is screened constructive help if an abnormality is found.9 There is no personal gain for an asymptomatic person to be converted into a patient by detecting an unidentified but untreatable condition. However now, with information from the human genome, this matter may need to be revisited. People other than the person screened profess an interest in genetic information when considering contracting life insurance policies. Genetic counselling may empower individual action that can spare future generations from serious disorders, as has been done humanely with screening for the Tay-Sachs gene among prospective marriage partners in the Ashkenazi Jewish community.10 Thus the ethical context of screening has changed since the SELSS was conducted and this may bear upon the development of public policy. But again, assumptions should be tested and the example of the SELSS randomized controlled trial followed wherever possible.
Fourth, thinking more broadly, as Holland does in his reflections on this study, preventive medicine is evolving. Multiphasic screening was once a prominent point of enthusiasm for prevention through early detection. Now my opinion is that affluent countries have moved, allowing for the notable exceptions of immunization, HIV control and tobacco, away from population-based efforts in primary prevention. There is greater attention now on secondary prevention. This has followed brilliant pharmaceutical development of such agents as the statin lipid-lowering drugs. The power that medicine and the pharmaceutical giants can exert over the supply of these demonstrably effective agents and others like them, both by clinical prescription and by advocacy for their cost subsidy by governments, makes them an attractive option to the hard work of environmental or individual lifestyle change, and to all-of-government approaches to health gain through primordial prevention and community development.
However, in less affluent countries, these secondary preventive options are simply not affordable. Health promotion is thus now challenged to develop ways to match the commercial reach of globalization through efforts to combat the effects of widening gaps between technology-rich and technology-poor societies. As Jeffrey Sachs, Director of the Centre for International Development and Professor of International Trade at Harvard University, wrote in The Economist 'in our Gilded age the poorest of the poor are nearly invisible'.11,12 Seven-hundred million people live in the 42 so-called Highly Indebted Poor Countries where a combination of 'extreme poverty and financial insolvency marks them for a special kind of despair and economic isolation'. Sachs comments that:
All the rich-country research on rich-country ailments, such as cardiovascular diseases and cancer, will not solve the problems of malaria. Nor will the biotechnology advances for temperate-zone crops easily transfer to the conditions of tropical agriculture. To address the special conditions of the Highly Indebted Poor Countries, we must first understand their unique problems, and then use our ingenuity and co-operative spirit to create new methods of overcoming them.
The SELSS was a major step forward in health services research. Not only did it answer an important question about the cost and value of multiphasic screening within the public sector, it demonstrated that health service research can be done to a high order of rigour, and despite all that is said about the irrelevance of epidemiology to the development of health policy, it made a difference.
Acknowledgments
I am grateful to Amanda Dominello for assistance in writing this opinion piece.
References
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