By Devon Zander
Peer Reviewed
Much has been said about the art of taking a patient history. The aphorism most commonly invoked by medical educators is that “80% of diagnoses can be made by history alone.”¹ Having heard this statement time and time again in lectures and on the wards, I began to wonder if this meme, often repeated but never cited, had any data behind it. More specifically, did this number come from a specific study? And, if so, has it ever been verified? Thinking about and investigating these questions took me on a literature journey that began in 1947.
Writing an essay that year in The Lancet, Robert Platt strove to demonstrate the importance of a good patient history in the formation of a diagnosis by breaking 100 of his patient encounters into three discrete steps (history, physical exam, and additional investigations such as imaging or laboratory work) and writing down his putative diagnosis after each step. For 68 of the 100 patients, his initial diagnosis, taken after just the history, was the same as his final diagnosis, the one made after any additional investigations. For an additional six patients, the diagnosis was “substantially correct” [italics his], meaning that in 74 out of the 100 patients (74%) the history correctly predicted the final diagnosis.²
In the years since, Platt’s conclusion and methods have continued to be tested–first in 1975 by J.R. Hampton and colleagues, who had outpatient physicians make a short differential for a sample of patients and rank their confidence in each diagnosis after reading the patient’s referral letter, taking a history, and doing a physical exam. The authors demonstrated that in 66 of the 80 patients studied (82.5%), “the medical history provided enough information to make an initial diagnosis of a specific disease entity which agreed with the one finally accepted.”³ This same idea was tested in 1980 by Gerald Sandler, who found that, although the diagnostic value of the history varied with the nature of the chief concern, in over 350 of the 630 patients studied (56%), the history was decisive in formulating a diagnosis.⁴ In 1992, Hampton’s original framework was replicated in Salt Lake City, with the history in 61 of 80 patients (76.3%) leading to the final diagnosis.⁵ A similar proportion of diagnoses (77 of 98; 78.6%) were made from history alone in a 2000 work published in the Journal of the Association of Physicians of India.⁶ And, most recently, in a UCLA neuro-ophthalmology clinic in 2009, Michelle Wang and colleagues found that 88% of a sample of 115 patients had diagnoses that matched the final accepted diagnosis after just the chief complaint and patient history were heard.⁷
What surprised me most in reading this literature was how close these estimates were to each other with regard to the effectiveness of using a patient history alone to make a diagnosis (mean 75.9%; 95% CI 67.9% to 83.9%). In addition to the effectiveness seen above, many of the authors made additional observations about the advantages of a good history–that it is cost-effective² and essential to the physician-patient relationship–and therefore necessary to teach well.
Some limitations of exclusively using a history were also acknowledged: first, that the history comes first in the sequence of creating a diagnosis and thus paves the way for later steps;² second, a history can often not be taken in an emergency or in a patient unable to express themselves, thereby increasing the role of an exam and additional studies in those situations;³ third, a patient history is not merely a history, it also encompasses the patient’s tone, general appearance, and all that is unsaid in an encounter;²,⁵ fourth, the history has different import in different specialties, just as the physical exam is more or less enlightening in certain fields (e.g., dermatology versus nephrology).¹,⁵ And finally, multiple authors were careful to note that all pieces of the encounter can be essential; the diagnosis from a history is often merely a hypothesis that gets tested or confirmed with further investigations.²,⁵ Ultimately, it was stressed that this is the essence of creating a differential: it needs to be further refined. In Platt’s original words (1947), “it is quite impossible for an intelligent physician to take a history without diagnostic possibilities being presented to his mind.”²
Practicing in the recent COVID pandemic has only continued to emphasize the importance of good history-taking, as social distancing has made televisits commonplace and reinforced how “the ‘history is the most powerful diagnostic tool available to the internist.’”⁵
To close, my doubts about the origins of the above aphorism have largely been assuaged. But, if I were to rewrite it a bit more accurately, it might be this: “75.9% ± 8% of diagnoses can be made by history (and sometimes referral letter) alone.”
Devon Zander is a 2nd year medical student at NYU Grossman School of Medicine
Peer reviewed by Michael Tanner, MD, associate editor, Clinical Correlations
Image courtesy of Wikimedia Commons, source: File:Patient Satisfaction.png|Patient_Satisfaction
References
- Cooke G. A is for aphorism–Is it true that ‘a careful history will lead to the diagnosis 80% of the time’? Aust Fam Physician. 2012;41(7):534-534. https://www.racgp.org.au/afp/2012/july/a-is-for-aphorism/. Accessed April 20, 2021.
- Platt R. Two essays on the practice of medicine. Lancet. 1947;2(6470):305-307. doi:10.1016/s0140-6736(47)90291-2 https://pubmed.ncbi.nlm.nih.gov/20257917/
- Hampton JR, Harrison MJ, Mitchell JR, Prichard JS, Seymour C. Relative contributions of history-taking, physical examination, and laboratory investigation to diagnosis and management of medical outpatients. Br Med J. 1975;2(5969):486-489. doi:10.1136/bmj.2.5969.486
- Sandler G. The importance of the history in the medical clinic and the cost of unnecessary tests. Am Heart J. 1980;100(6 Pt 1):928-931. doi:10.1016/0002-8703(80)90076-9 https://pubmed.ncbi.nlm.nih.gov/7446394/
- Peterson MC, Holbrook JH, Von Hales D, Smith NL, Staker LV. Contributions of the history, physical examination, and laboratory investigation in making medical diagnoses. West J Med. 1992;156(2):163-165.
- Roshan M, Rao AP. A study on relative contributions of the history, physical examination and investigations in making medical diagnosis. Abstract. J Assoc Physicians India. 2000;48(8):771-775.
- Wang MY, Asanad S, Asanad K, Karanjia R, Sadun AA. Value of medical history in ophthalmology: A study of diagnostic accuracy. J Curr Ophthalmol. 2018;30(4):359-364. doi:10.1016/j.joco.2018.09.001 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6277212/