Weighing medical evidence on a historical scale
Philip K. Wilson
In 1992, a clinical discipline emerged under the name Evidence-based Medicine (EBM). Now well-known, EBM refers to the "conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients" (Sackett). Clinical expertise is combined with newly supported biomedical evidence obtained through systematic literature searches to ensure the delivery of the highest quality health care. EBM also incorporates a "thoughtful identification and compassionate use of [the] patients' predicaments, rights, and preferences in making clinical decisions about their care" (Sackett).
EBM's current popularity gives the impression that it is a newly-devised methodology for improving patient treatment and care. However, while technologies and processes for compiling data may have changed over time, the system that EBM espouses to improve medical practice is not entirely new. Francis Bacon argued for the incorporation of evidence derived from the experimental method into medical practice in the early 17th century—heavily influencing the ongoing discussion of medical practice in 18th– and early 19th-century medical literature and providing the foundation for EBM as we know it today.
Francis Bacon's Novum Organum (1620)—the "new instrument of scientific method"—provided a framework for the experimental method. This method provided an organized search of natural phenomena, moving through progressive stages until certainty was reached (Prior). If science proposed, as Bacon argued, to give humans mastery over nature, thereby extending both their knowledge and their power, then the laws of nature must be better understood. He claimed this understanding was attainable by shifting science from deductive reasoning towards an inductive approach coupled with experimentation. Such an approach for the new authoritative voice of science provided a foundation upon which successive generations of physicians added support, albeit piecemeal, for medical practices based upon what they deemed as "evidence."
Bacon's inductive "method of interpreting nature" involved the assembly of a "sufficient . . . accurate collection of instances," or evidence, gathered "with sagacity and recorded with impartial plainness . . . from which, after viewing them in all possible lights, to be sure that no contradictory . . . [evidence] can be brought, some portion of useful truth," general law, or hypothesis will be established (Mallet). According to Bacon, natural philosophers (i.e., scientists) who relied solely upon the authority of the past—then the ancient logic (or Organon) of Aristotle—failed to advance new understandings of nature. Bacon advocated his method as freeing science from the "paralysing dependence of previous students of nature on the rough and ready conceptual equipment of everyday observation" (Quinton).
Hippocratic writings incorporated inductive reasoning in that diagnoses stemmed from developing a general hypothesis based upon carefully observing specific signs and symptoms. Yet according to Bacon, Hippocratic doctrine had become "more professed than labored" by the early 1600s, leading him to question whether or not contemporary practices yielded the best outcomes. Bacon specifically objected to Elizabethan physicians practicing medicine more according to a one-size-fits-all theory rather than to an individualized patient approach as Hippocrates had envisioned.
One 17th-century practitioner, Thomas Sydenham (later dubbed the "English Hippocrates"), similarly opposed theory-based medicine, claiming instead that medicine should be practiced by objectively gathering signs and symptoms without prematurely speculating upon their significance. Then, only after distinguishing useful signs from red herrings would the true understanding of a disorder become realized. Following an inductive diagnosis, expected disease patterns could be deduced. The London surgeon and physician Daniel Turner echoed Sydenham in the following century, claiming disease was not a priori predictable according to natural law, theory, or hypothesis. Physicians were not like natural philosophers who were free to apply rules "to Bodies inanimate, or putting simple Fluids into . . . Balance . . . [or] counting . . . Pressures or Impulses." Rather, they are dealing with human lives. Physicians, he asserted, must not "sacrific[e] Men's Lives" for the sake of some "meer [sic] Hypothesis" (Turner, vol. 2).
As a result of Bacon's influence, 18th-century practitioners increasingly relied upon a systematic collection and evaluation of testimonial evidence to discern the efficacy of remedies. James Jurin, for example, gathered testimonials in "good Baconian fashion," tabulated the results, and based his conclusions upon numerically demonstrable "matters of fact." Through numerical representations, a patient's anonymity could be maintained, a focus on success sidestepped religious and ethical debate, and charges of quackery were squelched. The numerical method made particular practices appear "more . . . legitimate" (Rusnock). The focus on evidence-based medicine was so strong during this period that historian Uhlrich Tröhler—in a critical examination of quantification in 18th-century therapies—derived his book title, To Improve the Evidence of Medicine, from a similarly titled 1793 publication by the distinguished London physician George Fordyce.
"Experience" and "experiment," two synonymous Romance language expressions, were used interchangeably in discussing Bacon's vision of evidence, which eventually became applied to health care. For Bacon, "ordered experience," founded upon methodological investigation, measurable criteria, and objectivity, counted as evidence; whereas "ordinary experience," based solely upon chance observation and subjectivity, did not (Tröhler). Considerable medical decision-making according to these standards was practiced in the 18th century. As an example, John Millar, a practitioner at the Westminster Dispensary, claimed in 1777 that "arithmetical calculation" provided "incontestable evidence" of one therapy's benefit over another. He deemed that individual case reports, no matter how "numerous and well attested" were "insufficient to support general conclusions." However, "by recording every case in a public and extensive practice, and comparing the success of various methods of cure with the unassisted efforts of nature," some "useful information may be obtained; and the dignity of the profession may be vindicated from vague declaration and groundless aspersions." Where "mathematical reasoning can be had," Millar concluded, "it is [as] . . . great [a] folly to make use of any other [method], as to grope for a thing in the dark, when you have a candle standing by you."
Relying upon large data sets instead of merely one single practitioner's experience was also significant. As Scottish naval surgeon Robert Robertson argued, "Few practitioners in physic will have so many cases come under their care . . . and consequently . . . few readers will ever have experimental authority to deny the validity of particular remedies." Still, small scale experiments were viewed to be of some importance, as seen in the comparative clinical trials to cure scurvy. James Lind's success, published in 1753, in treating scorbutic sailors (giving them "two oranges and one lemon daily for six days") was based on a very small-scale trial. Comparative methods on a larger sampling of patients, including the sailors aboard James Cook's voyages, suggested that the Irish physician David MacBride's recommendation of "wort" (i.e., unfermented malt) in the diet appeared the most promising preventative. Still, Lind persisted with "clinical trials" for another 20 years, tending upwards of 400 scorbutic patients a day in England's Haslar Hospital during the Seven Years' War (1756–63). In 1772, his arithmetic persuasion won the day. As he reflected:
A work . . . more perfect, and remedies more absolutely certain might perhaps have been expected from an inspection of several thousand scorbutic patients, from a perusal of every book published on the subject, and from an extensive correspondence with most parts of the world . . . but, though a few partial facts and observations may for a little [time], flatter with hopes of great success, . . . [an] enlarged experience must ever evince the fallacy of all positive assertions in the healing art (Lind).
George Guthrie, a British surgeon active during the Peninsular War, did not trust any "theory or opinion of authors not supported by actual experience." Regarding the immediacy of amputation on the battlefield—a critical concern for surgeons of the Napoleonic Wars—he recommended what we would recognize as a prospective comparison study: "It is not sufficient to perform twenty amputations on the field of battle, and contrast them with as many cases of amputation, done at a later period," he argued. The "twenty cases for delayed operation must be selected on the field of battle, and their result compared" some time later. Only through such comparison, he concluded, would "the value of the two modes . . . be duly estimated" (Guthrie).
British healers of the 1700s promoted new types of evidence in their campaigns for medical reform. They demanded "adequate empirical evaluation of existing and [newly] proposed . . . remedies." Doing so required "extensive, comparative trials, with results expressed by numbers." They "wished to base clinical medicine on elementary numerical analysis of compilations of observations made on distinct groups of patients." Their "observational analyses" of the efficacy of their treatments employed mortality statistics, administrative returns, and personal case histories that included both "one clinician's experience with patients receiving a particular treatment, as well as compiled statistics describing the experience of several clinicians" in treating the same disorder (Tröhler 115).
The quest for more practical information gave rise to hospital-based practices in the 1700s and the "Birth of the Clinic" in the early 1800s. In both types of institutions, the usefulness of evidence expanded from diagnosis to treatment. The "evidence" of particular treatments was increasingly represented in arithmetic ratios. For Paris hospital surgeon Pierre Charles Alexandre Louis, this numerical method—or medical arithmetic—became synonymous with scientific reasoning. The clinician reasoned by "employing aggregative thinking about a population of sick individuals rather than using pathological anatomy to observe disease in a particular individual." By emphasizing "quantitative thinking at the level of the social group rather than on qualitative understanding at the level of the individual patient," Louis was "appeal[ing] to the authority of number to justify clinical judgment" (Matthews). With the triumph of the numerical method, Louis argued, "No treatise whatsoever will continue to be the sole development of an idea." Rather, once an "analysis of a[n] . . . extensive series of exact detailed facts" furnishes answers to "all possible questions," therapeutics will "become a science" (Louis). Westminster Dispensary physician Francis Bisset Hawkins made a similar claim in his 1829 work entitled Elements of Medical Statistics. There is "reason to believe that a careful cultivation of [statistics], in reference to the natural history of man in health and disease, would materially assist the completion of a philosophy of medicine. . . . Medical statistics affords the most convincing proofs of the efficacy of medicine" (Hawkins).
Credible sources abound suggesting that particular elements of what we regard as EBM existed in previous eras. Today, EBM practices rely upon internet abstracting services and international consortia such as the Cochrane Collaboration to systematically cull pertinent information from the ever expanding warehouse of knowledge. Abridgements and abstracts of medical cases, though, have been published for centuries, among the earliest being the 1745 abstract of key articles published in the Royal Society's Philosophical Transactions. Thomas Southwell's abridgement of medical breakthroughs presented before the Royal Academy of Science of Paris appeared in his Medical Essays and Observations in 1764. Since the 1700s, abstracting key medical discoveries has escalated in parallel to the rise of medical periodical publishing. Many of these abstracts reflect the growing importance of surveying a series of multiple cases and analyzing them with statistical methods. For younger physicians, then and now, whose catalogue of personal experiences does not always meet their decision-making needs, relying upon abstracts has long been critical to their practices. Now more than ever, physicians have the ability to fulfill what were only dreams of bygone eras to cull pertinent information from vast databases of practices. Many today envision what Irish physician William Black argued in his Arithmetic and Medical Analysis of the Diseases and Mortality of the Human Species over two centuries ago, that an evidence-based medical arithmetic will be the dawn of a new era of medicine (Tröhler 117).
In sum, an historical review of the use of "evidence" is pertinent since EBM is quintessentially history-based medicine. Historians work detective-like, piecing together information from past events, sifting through red herrings as they seek for the best evidence upon which to base their interpretation (Becker). In essence, diagnosis is a historiographical practice. Like the development of a persuasive and accurate historical account, EBM carefully critiques a wide range of information in order to distinguish credible from incredible sources. Like the reputable historian, the EBM-guided physician has, through assimilating sources and ascertaining their validity, developed solid reasons for pursuing particular pathways of diagnosis (interpretation). Treatment has evolved through laborious trial and error methods, and thus, like diagnosis, may also be viewed as a historical process. Today, EBM is most often directed toward securing the best treatment from a host of historically produced possibilities.
Becker, C. L. "What is evidence? The relativist view—'everyman his own historian.'" The historian as detective: essays on evidence. Ed. R. W. Winks. New York: Harper Colophon Books, 1970.
Fordyce, G. "An attempt to improve the evidence of medicine." Transactions of the Society for the Improvement of Medical and Chirurgical Knowledge 1 (1793): 243.
Guthrie, G. J. On gun-shot wounds of the extremities. London: Longman, Hurst, Rees, Orme and Browne, 1815. 39.
Hawkins, F. B. Elements of medical statistics. London: Longman, 1829. 2–3.
Lind, J. A treatise on the scurvy. 3rd ed. London: Crowder, Wilson, Nicholls, Cadell, Becket, Pearch and Woodfall, 1772. v-vi.
Louis, P. C. A. Researches on the effects of bloodletting in some inflammatory diseases, and on the influence of tartarized antimony and vessication in pneumonitis. Trans. Putnam, C.G. Boston: Hillard, Gray, 1836. 70.
Mallet, D. The life of Francis Bacon, Lord Chancellor of England. London: Millar, 1740. 93.
Matthews, J. R. Quantification and the quest for medical certainty. Princeton: Princeton University Press, 1995. 19.
Millar, J. Observations on the prevailing diseases in Great Britain. 2nd ed. London: Millar, 1798. 76.
Prior, M. E. "Bacon's man of science." Journal of the History of Ideas 15 (1954): 348–70.
Quinton, A. Francis Bacon. Oxford: Oxford University Press, 1980. 55.
Robertson, R. Observations on the jail, hospital, or ship fever. London: Murray, 1783. 312.
Rusnock, A. A. "The weight of evidence and the burden of authority: case histories, medical
statistics, and smallpox inoculation." Medicine in the Enlightenment. Ed. Porter, R. Amsterdam: Rodopi, 1995. 289–315.
Sackett, D.L., et al. "Evidence-based medicine: what it is and what it isn't." British Medical Journal 312 (1996): 71.
Tröhler, U. To improve the evidence of medicine: the 18th century British origins of a critical approach. Edinburgh: Royal College of Physicians of Edinburgh, 2001. 1–2.
Turner, D. "Discourse concerning fevers." London: Oake, 1727. 28–29, 58, and D. Turner, Art of surgery. Vol 2. London: Rivington, Lacy, and Clarke, 1725. 75.
PHILIP K. WILSON, PhD is a medical and science historian at Penn State's College of Medicine in Hershey, Pennsylvania, where he is a professor of Humanities and Science, Technology & Society. He is also the director of The Doctors Kienle Center for Humanistic Medicine. His historical scholarship includes the areas of disease, heredity, life science, earth science, and the interactions between science and religion.
Winter 2012 | Sections | History Essays