Diagnosis: What Doctors Are Missing

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University of Pennsylvania, Philadelphia
Thomas Eakins: The Agnew Clinic, 1889

Several months ago, I led a clinical conference for interns and residents at the Massachusetts General Hospital. It was thirty-three years since I had trained there, and beyond discussing the topic of the gathering, I was keen to learn from these young doctors how they viewed recent changes in the culture of medicine.

The subject of the conference centered on how physicians arrive at a diagnosis and recommend a treatment—questions that are central in the two books under review. We began by discussing not clinical successes but failures. Some 10 to 15 percent of all patients either suffer from a delay in making the correct diagnosis or die before the correct diagnosis is made. Misdiagnosis, it turns out, is rarely related to the doctor being misled by technical errors, like a laboratory worker mixing up a blood sample and reporting a result on the wrong patient; rather, the failure to diagnose reflects the unsuspected errors made while trying to understand a patient’s condition.

These cognitive pitfalls are part of human thinking, biases that cloud logic when we make judgments under conditions of uncertainty and time pressure. Indeed, the cognitive errors common in clinical medicine were initially elucidated by the psychologists Amos Tversky and Daniel Kahneman in their seminal work in the early 1970s. At the conference, I reviewed with the residents three principal biases these researchers studied: “anchoring,” where a person overvalues the first data he encounters and so is skewed in his thinking; “availability,” where recent or dramatic cases quickly come to mind and color judgment about the situation at hand; and “attribution,” where stereotypes can prejudice thinking so conclusions arise not from data but from such preconceptions.

A physician works with imperfect information. Patients typically describe their problem in a fragmented and tangential fashion—they tell the doctor when they began to feel different, what parts of the body bother them, what factors in the environment like food or a pet may have exacerbated their symptoms, and what they did to try to relieve their condition. There are usually gaps in the patient’s story: parts of his narrative are only hazily recalled and facts are distorted by his memory, making the data he offers incomplete and uncertain. The physician’s physical examination, where he should use all of his senses to try to ascertain changes in bodily functions—assessing the tension of the skin, the breadth of the liver, the pace of the heart—yields soundings that are, at best, approximations. More information may come from blood tests, X-rays, and scans. But no test result, from even the most sophisticated technology, is consistently reliable in revealing the hidden pathology.

So a doctor learns to question the quality and significance of the data he extracts from the medical history of the patient, physical examination, and diagnostic testing. Rigorous questioning requires considerable effort to stop and look back with a discerning eye and try to …

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