Department of Preventive Medicine, Northwestern University Medical School, Chicago, Illinois, USA.
The report of the South-East London Screening Study1 neatly exemplifies the research paradox described recently by Stephen Jay Gould: ... straightforward facts enshrouded in difficult or ambiguous meanings'.2 In a randomized controlled trial of people, baseline ages 4064 years, from two South-East London general practices, two multifactor screenings 2 years apart (19671968 and 19691970) were associated with no significant differences between Screened and Control groups in 5-year incidence of disease morbidity or in 9-year rates of GP consultations, hospital admissions, certified sickness work absenteeism, or mortality. Straightforward data! But what do they mean? What conclusions can be drawn from them? Based on the last sentence of the report, the authors are apparently sure they have the answer: down with multiphasic screening of the middle-aged in general practice. But for this commentator, Gould's words fit: straightforward facts enshrouded in difficult or ambiguous meanings'.2
Why? The nub of the problem is embedded in the statement of Study purpose: ... assess the value, if any, of introducing a general practice based screening service for 4064-year-olds as an extension of the existing National Health Service'.1 Broad, general, vague; it could mean a multitude of things. And that's it as to aims; no specific prior hypotheses or questions are stated. To get some idea about what the authors actually had in mind, one has to go through Methods and Results step-by-step.
That effort sheds light on some specifics, but leaves others in the dark. Thus:
In this regard, the authors' observation in Discussion is relevant: The screening service ... appeared to have been generally well received by the population ...'.1 Too bad that for the NHS patients the apparent inadequacy of the interventions resulted in a lost opportunity. Relevant also in this regard is the authors' statement as to costs: ... a relatively low figure, ... approximately a fifth of that charged by private screening organizations in the UK ...'.1 From this commentator's limited knowledge about such private efforts in the UK, they serve the more affluent social strata (social classes I and II), which make up a small minority of the South-East London practices (Table 1). Their services are generally extensive, including health education, motivation, referral, and follow-up.
Again, the social context is relevant. During the post-World War II decades, social classes in the UK experienced similar trends in the coronary epidemicwith death rates initially higher for those of lower than for those of higher social classes, latterly with declining rates for the higher social classes, but plateaued or rising rates for lower social classes, with a consequent increase in the socioeconomic status (SES) gap. And, correspondingly, more adverse levels of major risk factors in those of lower SES e.g. smoking, blood pressure. The South-East London Study dealt mostly with patients from social classes IIIV.
We are now in a new centurymore than 30 years since the South-East London Study was launched. Much that may have seemed equivocal in 19671968 is now crystal clear e.g. as to the number one problem: epidemic CVD and the role of lifestyle-related major risk factors (my area of expertise). Their impact on CVD risks is continuous, strong, graded, independent, combinative and aetiologically significant. They can be prevented and controlled by safe nutritional-hygienic measures plus modern pharmacotherapy as indicated. The population is interested in their prevention and control, and (paced by higher socioeconomic strata) has acted favourablyalbeit in a limited way stillto improve matters, despite the paucity of resources brought to bear to accomplish this, and the noise in the system' from vested commercial interests. At least from the US national surveys by the Department of Agriculture in the 1960s, improvements in lifestyles, specifically eating patterns, are attributable mainly to influences on the population from two sourceshealth professionals and the mass media. These improvements, and their favourable impact on such major risk factors as serum cholesterol and blood pressure, account significantly for declining CVD death rates.
With this as background, what in the year 2001 is to be concluded about the South-East London Screening Study? At national and international CVD meetings, sessions are organized, particularly for clinicians, on How to ...'. The South-East London Screening Study is a historically useful case report on How not to ...'. It shows that a screening service is in fact not a treatment; contrary apparently to the authors' original concept, screening is a means to an end, not an end in itself. It can be useful when related components are in place to optimize the effort before, during, and afterand especially when, by virtue of sound national public policy and resources made available for sustained implementation of that policy, the societal context aids and abets the efforts of physicians and other health professionals, including their screening efforts.
To conclude, screening in general practice does not serve, despite support by the population, when done as in the South-East London Study in the 1960s (in the societal context of that time), and with virtually no resources available to the NHS general practices to intervene effectively with patients in relation to screening efforts and results.
Given the specifics of this very particular, limited, dated study, its negative results are not generalizable. Its findings cannot be soundly interpreted as an evidence-based foundation for the authors' concluding generalizationsweeping, unqualified, over-reaching, absoluteagainst all screening in general practice. That is simply warmed-over dogma.
As we first learned in the 19th and early 20th centuries in regard to epidemic infectious and undernutritional diseases, and then learned again in the second half of the 20th century in regard to epidemic non-infectious CVD and neoplastic diseases, their prevention and control is a sustained complex process, motley, variegated, involved, proceeding at multiple societal levels. The health care services sector is one of those levels, an important one, and screeningsoundly employedis one (among many) of its useful tools.
References
1 The South-East London Screening Study Group. A controlled trial of multiphasic screening in middle-age: results of the South-East London Screening Study. Int J Epidemiol 1977;6:35763.[Abstract]
2 Gould SJ. Tales of a feathered tail. Natural History2000; 109(9)(November)3242.