Tribute to alvan r. feinsteinClinical epidemiology: what, who, and whither
Introduction
For someone who loved words (especially arcane “new” ones constructed from bits of “old” languages), Alvan Feinstein's choice of “clinical epidemiology” to describe his thoughts and deeds was, uncharacteristically, both immediately pronounceable and transparent. Nonetheless, the term deserves (the Editor thinks) and rewards (I think) a brief etymologic exploration of both the origins of its meaning and their changes with time. Its continuing evolution exposes the disutility of “essentialism,” the notion that words have a single, immutable meaning. On the contrary, the changes in the meaning of clinical epidemiology over the past 6 decades vigorously reinforce the “nominalist” view that definitions are best read from right to left.
In this essay, I shall summarize my understanding of the origins of clinical epidemiology before my time and describe its reintroduction and evolution after my arrival on the scene in 1963, with comments along the way on the central role Alvan Feinstein played in its continuing development and in the inspiration and mentoring of so many of its practitioners. I will integrate Alvan's contributions with those of the other people, institutions, and journals that played major roles in the development of the field and its offspring.
I reckon that credit for the first appearance of clinical epidemiology in the medical literature goes to John Paul (1893–1971), an infectious disease internist who was appointed head of the Section of Preventive Medicine in Yale's Department of Medicine in 1940. In his president's address to the American Society for Clinical Investigation in 1938 (when it was still an organization with broad interests that included intact humans), he proposed clinical epidemiology as a “new basic science for preventive medicine” in which the exploration of relevant aspects of human ecology and public health began with the study of individual patients” [1].
John Paul also gets the credit for the first use of the term clinical epidemiology as the title for both a book and a course for undergraduate medical students [2]. Once again, it had a population rather than individual patient orientation in which he described the role of the clinical epidemiologist as being “like that of a detective visiting the scene of the crime” who then “branches out into the setting in which that individual became ill.” Thus, the procedure in his course for third and fourth year Yale medical students was to “start the student at the bedside and lead him gradually away from it” (italics mine). This was in sharp contrast to the orientation of pioneers like William Silverman and Thomas Chalmers who, although they did not refer to themselves as clinical epidemiologists, exemplified its application in bedside neonatology [3] and gastroenterology [4].
The shift in the focus of clinical epidemiology from community ecology to individual patients and groups of patients took place in the 1960s, and I have long-attributed its Canadian branch to the combined influences of Nikita Khrushchev and Alvan Feinstein [5]. The former, by placing missiles in Cuba, precipitated the drafting of thousands of American junior clinicians into the armed forces and U.S. Public Health Service, where we were torn from the bedside and forced to work in and think about public health ventures. Despondent over the interruption in my career as an academic nephrologist, I came upon Alvan's article on Boolean algebra and clinical taxonomy [6], and wrote him a fan letter. Thus began a relationship that led both of us to McMaster University in Canada (Alvan for 2 years and me for 27), and witnessed the development of clinical epidemiology in each of our respective countries and beyond.
My mentorship under Alvan began with a series of letters and conversations, often by no means cordial, in which we hammered out our separate (but overlapping) concepts of what clinical epidemiology should be and how it should be practiced. As I've described elsewhere, during his 2-year Visiting Professorship and ongoing stewardship of our McMaster efforts, Alvan “brought both science and intrepidity to our fledgling department (and did his best to make us presentable to the academic gentility)” [7].
With Alvan's encouragement, the first Clinical Epidemiology Research Unit in the new era was established at the State University of New York at Buffalo in 1966, followed shortly by the Department of Clinical Epidemiology and Biostatistics at McMaster in 1967 [8]. In the prospectus for each of them I defined clinical epidemiology as “the application, by a physician who provides direct patient care, of epidemiologic and biostatistical methods to the study of diagnostic and therapeutic processes in order to effect an improvement in health” [9]. Thus, at McMaster the external, public health orientation was set aside and replaced with a focus on individual patients and groups of patients in clinical, not community, settings.
In 1968, Alvan published his landmark series on clinical epidemiology in the Annals of Internal Medicine 10, 11, 12. It was a logical extension of his book, Clinical Judgment [13], published the previous year, although the book did not employ the term clinical epidemiology. In the Annals series he defined the “territory” of clinical epidemiology as: “the clinicostatistical study of diseased populations. The intellectual activities of this territory include the following: the occurrence rates and geographic distribution of disease; the patterns of natural and post-therapeutic events that constitute varying clinical courses in the diverse spectrum of disease; and the clinical appraisal of therapy. The contemplation and investigation of these or allied topics constitute a medical domain that can be called clinical epidemiology” [14]. Thus, he cast a wider net, and included elements of classical “big E” epidemiology and public health. (In an effort to maintain my clinical skills while a graduate student at Harvard, I worked nights examining patients for William Kannel at the Framingham Study. When I first encountered Dr. William Castelli, a long-time Framingham investigator, he adopted the stance and voice of W.C. Fields and inquired: “Sonny, have you matriculated at Harvard in order to become one of those ‘big E’ epidemiologists, or are you actually going to get your hands dirty here in Framingham with us “little E” epidemiologists?” Alvan's inclusion of public health in his definition of clinical epidemiology was repeated 18 years later in his book of that name: “clinical epidemiology represents the way in which classical epidemiology, traditionally oriented toward general strategies in the public health of community groups, has been enlarged to include clinical decisions in personal-encounter care for individual patients” [15] (emphasis mine).
Over the next several years, Alvan led the development of clinical epidemiology in the United States and throughout much of the world. A recurring theme and focus of his group at Yale was the careful observation and measurement of clinical phenomena (his term “clinimetrics” [16] and Mary Charlson's “comorbidity” [17] came into common use), especially in the description and prediction of prognosis [18] but also, with David Ransohoff, in diagnosis [19]. In Canada and the UK, the emphasis was directed rather more toward evaluating therapy, with major scientific attention devoted to improving the validity and credibility of the randomized clinical trial when applied to both groups [20] and individual patients [21], and, once benefit was determined, toward compliance with efficacious health care [22].
A Fellowship in clinical epidemiology had already begun at Yale, and a degree-granting program began at McMaster in 1970. Opportunities for clinicians to obtain education and training in clinical epidemiology gradually spread to other North American health sciences centers and to centers in Europe and the Far East. (For example, by 2001, 15 of the 16 Canadian medical schools offered graduate training in clinical-practice research methods.)
Combined training in clinical medicine and clinical epidemiology greatly expanded in the United States in 1974 with the creation of the Robert Woods Johnson Clinical Scholars Program (http://www.rwjf.org/reports/npreports/scholarse.htm).
The first modern textbook in clinical epidemiology was written by Robert Fletcher, Suzanne Fletcher, and Edward Wagner at the University of North Carolina, and came out in 1982 [23]. Now in its third edition, it continues to be a favored introductory text. It was followed by ones from McMaster (now in its second edition [24]) and Yale [25] in 1985, Seattle in 1986 (now in its second edition [26]), and McGill [27] in 1988. Each has its own flavor and niche, and they are now available in several languages.
The internationalization of clinical epidemiology received a huge boost in 1980 when Kerr White and the Rockefeller Foundation initiated the International Clinical Epidemiology Network (INCLEN) (http://www.inclen.org). In this program, young clinicians from low-income countries came for training in clinical epidemiology to “training centers” at McMaster in Canada, Newcastle in Australia, and the University of Pennsylvania. A key element of their career development was linkage to a mentor who spent part of each year working with them back at their home institutions. The organization now includes 64 medical institutions in 26 countries. Its most important accomplishments from my perspective have been the repeated redefinition of clinical epidemiology to suit local needs and the taking over of the training of clinical epidemiologists by regional centers in Africa, China, India, Latin America, and South East Asia.
The dissemination of clinical epidemiology to other high-income countries proceeded at different paces and with varying enthusiasm. It was quickly adopted in The Netherlands, with nearly simultaneous developments in Amsterdam (led by Harry Büller at the Academic Medical Center), Leyden (led by Jan Vandenbroucke at the University Medical Center), and Maastricht (led by André Knottnerus at the Faculty of Medicine, with a special focus on primary care research). Early on, Alessandro Liberati established a Clinical Epidemiology Unit at the Mario Negri Institute in Milan, and Les Irwig, Steven Leeder and Paul Glasziou led its development at the Universities of Sydney, Newcastle and Queensland in Australia. Its champions in the UK were mostly clinicians like Peter Sleight and Charles Warlow, and its expansion there was often resisted by the new Faculty of Community Medicine. Other countries like Germany, Spain, and South Africa were still dominated by “clinical authorities” who resisted the egalitarianism inherent in clinical epidemiology, and (with the exception of a few hospital-based clinical epidemiology units such as Francisco Pozo's in Madrid) it was not until the evidence-based medicine movement that the rapid, widespread adoption of these ideas occurred in such countries. [I am certain that I have not done justice to the development of clinical epidemiology outside North America. Some of this deficit will be corrected in a forth-coming book (J. Daly, Evidence-Based Medicine and the Search for Certainty in Clinical Care, New York and Berkeley: The Milbank Memorial Fund and the University of California Press), and I hope that readers will inform us about the development in their countries through Letters to the Editor.]
In the meanwhile, Alvan was making clinical epidemiology a respectable undertaking for North American academic clinicians. The most prestigious annual meetings of North American academic medicine were the American Federation for Clinical Research (the young squirts), the American Society for Clinical Investigation (the young turks), and the Association of American Physicians (the old farts). There was no place on their programs for clinical epidemiologists, so we borrowed an unused meeting room from them and held our own Sydenham Society meetings {Alvan, Tom Chalmers, and I organized the meetings, and Harold Conn kept us solvent) to discuss the methods and findings of clinical epidemiology. By 1972, Alvan's negotiating skills and political connections had led to the introduction of sections on Clinical Epidemiology at each of the societies, where they soon became their fastest growing scientific sessions. Alvan also managed the election of the first young clinical epidemiologists to these organizations, where they now comprise an impressive proportion of the membership.
Clinical epidemiology has not been without its detractors [28], especially among more traditional epidemiology departments who perceived (often correctly) their loss of resources and bright young minds to this new discipline. Perhaps the most radical and articulate of these is Walter Holland who, in 1983, urged us to abandon the term clinical epidemiology altogether [29]. Although acknowledging its usefulness over the previous 15 years, he now found it a divisive term that conferred “respectability” only on those epidemiologists who practiced medicine, created the impression that one form of teaching (using epidemiology for solving clinical problems) was more appropriate than another (mastering classical epidemiologic methods), and fashioned students' perceptions of the priorities and needs of societies. (Indeed, his own department bore that name for several years, in part because the inclusion of “clinical” in its title afforded higher salaries to its members. True to his convictions, he removed the word from the name of his department.)
I replied to Walter Holland's criticisms, first by emphasizing that the distinction between clinical and nonclinical epidemiologists was on a nominal, not ordinal, scale [30], and suggested that his other criticisms were not only true, but to be applauded: clinical epidemiology was a better way to teach medical students, and clinical epidemiology was reshaping the perceptions of not only medical students (who began to see it as a relevant basic science) but entire faculties (departments of clinical epidemiology were growing in number and size; clinical departments were carrying out more and better “clinical-practice” research [31]), and learned societies were acknowledging the relevance of clinical epidemiology to “clinical research” in ways that classical epidemiology had been unable to achieve.
Having established itself, gained formal recognition at universities, granting agencies, and learned societies, and populated academic departments and research groups around the world, the field of clinical epidemiology became increasingly able to emphasize its similarities to, rather than its differences from, classical public health epidemiology, and the related sciences of economics, political science, psychology, and sociology. As pointed out by Walter Spitzer [32], all of these disciplines carry out and collaborate in studies of “diagnostic and therapeutic processes in order to effect an improvement in health” [33], and the term's usefulness nowadays is perhaps greater in describing the “clinical epidemiologist” as the sort of academic clinician who, along with collaborators from an array of disciplines, carries out this sort research. (Indeed, one recent “clinical epidemiology” text was written by two biostatisticians: Knapp RG, Miller MC III, Clinical Epidemiology and Biostatistics. Baltimore: Williams & Wilkins, 1992.)
Clinical epidemiology has not evolved in a vacuum, and much of its growth, strength, and continuing evolution are the result of its leadership and participation in five other parallel evolutions (some of them revolutions) in evidence generation, evidence appraisal, evidence retrieval, evidence application, and evidence synthesis. Although a wide spectrum of clinical journals have published the concepts, methods and results of clinical epidemiological research, and The Journal of Clinical Epidemiology has been a natural home for the discipline, some individual general medical journals stand out in fostering the field and its recent evolutions. In the 1970s the Journal of Clinical Pharmacology and Therapeutics turned Donald Mainland's “Notes from a Laboratory of Medical Statistics” over to Alvan for his landmark series in “Clinical Biostatistics.” In the 1980s the Canadian Medical Association Journal hosted series on “How to Read Clinical Journals” and “How to Interpret Diagnostic Data” from Brian Haynes, Peter Tugwell, and our group at McMaster. In the 1990s, Drummond Rennie at the Journal of the American Medical Association and I collaborated in starting the “Rational Clinical Examination” series, currently edited by David Simel, that hosted reviews of the accuracy and precision of the clinical history and examination from clinical epidemiologists such as Alan Detsky, Richard Deyo, John Williams, Steven Grover, David Naylor, Sonia Anand, and Akbar Panju. Drummond went on to host the bell-weather series of “Users' Guides to the Medical Literature” led by Gordon Guyatt, and they collated the latter into a major text. Throughout this era, Ed Huth, followed by Robert and Suzanne Fletcher, Frank Davidoff, and now Harold Sox, have led Annals of Internal Medicine to champion the field, beginning with Alvan's 1968 papers on clinical epidemiology, including series such as the one on systematic reviews edited by Cynthia Mulrow and Deborah Cook [34], and culminating in Brian Haynes's creation of the ACP Journal Club and Evidence-Based Medicine series of journals of secondary publication. In the latter it was joined by the British Medical Journal, whose leadership, especially Richard Smith and Alexandra Williamson, helped explain our new world ideas about clinical epidemiology and evidence-based medicine to the old world, and nurtured their maturation and relevance for Europe and beyond.
Clinical epidemiology has played a central or major role in five recent evolutions (some say revolutions) in health care: in evidence generation, its rapid critical appraisal, its efficient storage and retrieval, evidence-based medicine, and evidence synthesis. The evolution in evidence generation since 1970, although most easily documented in the growth in reports of and about the randomized trial (with more of them published in the single year 2000 than in the decade 1965–1975), is paralleled by similar, although less spectacular, increases in the numbers and sophistication of reports about diagnosis, prognosis, and the appropriateness and quality of clinical care. Clinical epidemiologists are providing leadership in both the generation and continuing methodologic development of this burgeoning body of clinically relevant evidence.
The price to be paid for this vast increase in relevant evidence was an increasing difficulty in finding it, retrieving it, and keeping up to date with it. Although I doubt that the busy front-line clinician was able to keep up to date even in the 60s, by 1972 there were about 4 M articles published in the biomedical literature per year (in all languages) [35]. Restricting one's reading to just the journals that provide the content that is sound and relevant for internal medicine requires reading 33 articles every day of the year [36]. The dramatic decline in general medical knowledge after certification that was documented by a group of clinical epidemiologists at the University of Washington made it impossible to ignore this growing problem [37]. A second problem became evident when this growing body of evidence was subjected to the critical appraisal of its validity: the majority of it was found wanting. These two situations combined to place clinicians at increasing risks of “drowning in doubtful data.” The parallel evolutions in the rapid critical appraisal of evidence (for its validity and potential clinical usefulness) and in the efficient storage and rapid retrieval of evidence combined to rescue clinicians who were striving to track down the evidence than might help their patients. Although several clinical epidemiologists, as well as library scientists, statisticians, and qualitative researchers, made vital contributions to these parallel evolutions, it was Brian Haynes who rolled up his sleeves, provided both intellectual and organizational leadership, formed the teams, and endured a decade of inattention from granting bodies to bring these evolutionary streams together in powerful and clinically relevant ways 38, 39. The example he set by reducing the internal medicine literature to just the 2% that was both valid and clinically relevant in the ACP Journal Club (http://www.acpjc.org/Content/114/1/ISSUE/ACPJC-1991-114-1-A18.htm) introduced the revolution that today provides front line clinicians in a number of clinical fields with manageable chunks of up-to-date, reliable evidence, right at the bedside [40].
As more and more clinicians, armed with the strategies and tactics of clinical epidemiology, cared for more and more patients, they began to evolve the final, vital link between evidence and direct patient care. Building on the prior evolutions, and manifest in clinically useful measures such as Andreas Laupacis's NNT (the Number of patients a clinician would Need to Treat to prevent one more bad outcome) [41], and often incorporating the patient's own values and expectations as in Sharon Straus's LHH (the Likelihood that a treatment would Help vs. Harm the patient's achievement of their health objectives) [42], the revolution of Evidence-Based Medicine was introduced by Gordon Guyatt [43]. Since its first mention in 1992, its ideas about the use (rather than just critical appraisal) of evidence in patient care and in health professional education have spread worldwide, and have been adopted not only by a broad array of clinical disciplines (most recently in a new sort of house officers' guide edited by Christopher Ball and Robert Phillips [44]) but also by health care planners and evaluators.
Simultaneous with these other evolutions and revolutions, and both supporting and building upon them, has been the evidence-synthesis evolution of strategies and tactics for assembling and systematically reviewing the totality of evidence about the effects of health care. Generated from revelations such as Cynthia Mulrow's exposure of the sad state of the medical review article [45], and cautionary notes about subgroup analyses from Andrew Oxman and Gordon Guyatt [46], this evolution is epitomized in the Cochrane Collaboration Collaboration (http://www.cochranelibrary. com/), a worldwide collaboration of patients, clinicians, and methodologists who prepare, maintain, and promote the accessibility of systematic reviews of the effects of healthcare interventions. Conceived and led by Iain Chalmers, and with invaluable support from Muir Gray, this work has been characterized as equal in importance to the human genome project [47]. Although the conceptualization, operation, and ramifications of this evidence-synthesis evolution extend far beyond clinical epidemiology, the contributions of clinical epidemiologists to its success are, in my view, their greatest accomplishment since the term was introduced 65 years ago.
Section snippets
Potential competing interests
Dave Sackett has been wined, dined, supported, transported, and paid to speak by countless pharmaceutical firms for over 40 years, beginning with two research fellowships and interest-free loans that allowed him to stay to finish medical school. Dozens of his randomized trials have been supported in part (but never in whole) by pharmaceutical firms, who never received or analyzed primary data and never had veto power over any reports, presentations, or publications of the results. He has twice
Acknowledgments
Thanks to Iain Chalmers, Robert Fletcher, Gordon Guyatt, Brian Haynes, Richard Horton, Les Irwig, Roman Jaeschke, Andre Knottnerus, Regina Kunz, Finlay McAlister, Ann McKibbon, Andrew Oxman, Donald Redelmeier, David Ransohoff, Drummond Rennie, David Simel, Sharon Straus, Charles Warlow, and Merrick Zwarenstein for their comments on a draft of this article.
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