ARTICLE IN BRIEF
Investigators compared different approaches to teaching residents to conduct a neurological exam — and the results. Experienced clinicians discuss the merits of each exam type.
The medical student, after about 10 minutes of examining an actor trained to mimic a specific disorder, was asked by an observing physician, “Tell us what you're thinking.” “I haven't started thinking yet,” the student responded. “First I gather all the data, and then I start thinking about it.”
This exchange inspired Rachel Yudkowsky, MD, to join with Georges Bordage, MD, PhD, a colleague in the Department of Medical Education at the University of Illinois (UIC) College of Medicine, to develop what became known as the hypothesis-driven exam. The exam is designed to quickly elicit findings that support or refute the most likely diagnosis.
“Frequently what we teach students is a screening neurological exam,” said Dr. Yudkowsky, director of the Dr. Allan L. and Mary L. Graham Clinical Performance Center, and associate professor in the department of medical education at the UIC College of Medicine. “The problem is students learn to do it by rote. They learn the maneuvers, but they don't learn how to recognize and interpret abnormal findings. The hypothesis-driven exam encourages students to start thinking very early on.”
TEST FOR THE HYPOTHESIS EXAM
Now researchers at the University of California, San Francisco (UCSF) have provided some evidence that supports this assertion. As reported in a paper in the Sept. 7 online edition of Neurology, they divided 16 fourth-year medical students who had already completed a core clerkship in neurology into two groups and had them examine four patients, two of whom displayed deficits such as moderate hemiparesis and subtle proximal weakness, which could be evidence of an acute neurological problem. Eight of the students conducted the standard 30-minute neurological screening exam, while the other eight conducted a hypothesis-driven 30-minute exam that emphasized tailoring the exam based on a hypothesis about the cause of the deficits. The students were not allowed to interview the patients, and the patients were instructed not to answer questions.
The students who performed the hypothesis-driven exam identified 61 percent of specific abnormalities in a median time of seven minutes, while the students who performed a screening exam identified 53 percent in a median time of eight minutes.
The authors concluded that the hypothesis-driven approach achieved greater sensitivity in terms of identifying neurological deficits, and did so more quickly, but at the cost of lower specificity, or false positives.
“On the one hand, the higher specificity of the screening examination may result in fewer false findings and therefore less unnecessary testing and consultation, favoring its use in low-risk settings,” the authors stated. “On the other hand, a hypothesis-driven approach may be superior in acute situations with a high likelihood of serious disease, because higher sensitivity ensures that patients with focal lesions are reliably identified and referred for appropriate testing and treatment. Therefore, our study supports supplementing traditional methods of teaching the neurological examination with a hypothesis-driven approach.”
Although the hypothesis-driven approach proved slightly better, it is not intended to replace the traditional neurological screening exam, according to lead study author Hooman Kamel, MD, formerly with the UCSF but now an assistant professor of neurology at Weill Cornell Medical College.
“The screening exam is the bedrock of learning neurology,” Dr. Kamel told Neurology Today. “We just thought it would be helpful to complement the screening exam with a more structured approach that gives students more tools that help focus the exam. The motivation for this study was to help students going into fields other than neurology, because I think there's a lot of discomfort among non-neurologists when it comes to the neurological exam.”
The practicing neurologist, according to Dr. Kamel, often forms hypotheses before performing an exam. “We fluidly change the exam according to the situation we're in,” he said. “If we're in a time-sensitive situation, or if, based on the history, we're pretty sure of what's going on, we only test things that are relevant to what we think is happening. But that takes years of practice. Students are taught to do the whole neurological exam, but what they don't get is instruction on how to focus the exam if the situation calls for it. So if they're in a time crunch, or the history is indicating something specific, it's hard for them to know which elements of the exam to do and which not to do.”
CLINICIAN EDUCATORS WEIGH IN
Ralph F. Jozefowicz, MD, who was not involved with the study, noted that the participating students didn't take a history of the patients they examined. “I think the most important thing is taking a good history and listening to the patient,” said Dr. Jozefowicz, professor of neurology and medicine, and associate chair for education in the neurology department at the University of Rochester School of Medicine and Dentistry. “You always hear that 80 percent of the diagnosis comes from the history, 15 percent from the exam, and 5 percent from labs. Learning how to listen to the patient is the key. The patients try to tell you what's wrong, and you need to listen to them.”
Also, Dr. Jozefowicz believes the distinction between the screening exam and the hypothesis-driven exam is not entirely clear. “We all do a combination of the screening exam and the focused exam,” he said. “I think we should be teaching students how to think as they're doing the exam. I teach the screening exam, but I am constantly teaching the students how to interpret. You start with the chief complaint and generate the differential. Then you take the history and narrow the differential. You figure out what you're looking for during the examination.”
While both approaches have value, “the key is to know when to apply each approach,” said Barney J. Stern, MD, director of the neurology residency program at the University of Maryland School of Medicine. Applying all the knowledge needed to do a competent neurological exam may become easier with the advent of electronic records, he added. Pull-down menus, checklists, and other electronic aids might help non-neurologists use hypothesis-driven examination templates and follow the protocol for the neurological screening exam.
“I think the authors recognize that as we become more computer driven, these kinds of pull-down menus or templates may become ubiquitous,” Dr. Stern said.
In many circumstances a broad screening exam would be an appropriate choice, said Eric Cheng, MD, associate professor of neurology at the David Geffen School of Medicine at University of California, Los Angels, whose research focuses on the quality of care received by persons with neurological conditions. Such an exam doesn't cover any single area in a lot of detail, but the hypothesis-driven exam doesn't cover every area.
“A hypothesis-driven exam requires more thought, but this paper shows that a hypothesis-based exam is more likely to pick up abnormalities,” Dr. Cheng said. “A next step would be to figure out if non-neurologists can pick the correct hypothesis-based exam under time pressure, and if they can perform that focused exam correctly.”
Drs. Yudkowsky and Bordage have received an Edward J. Stemmler grant from the National Board of Medical Examiners to develop the hypothesis-driven exam as an alternative to the head-to-toe exam. In a 2009 paper in Medical Education they and their colleagues reported findings similar to those found by the authors of the Neurology study – 66 third-year medical students using a hypothesis-driven approach to the physical exam anticipated 65 percent of the findings for two plausible diagnoses developed before examining the patient. The authors concluded that the hypothesis-driven physical exam provided the students with “a thoughtful, deliberate approach to learning the physical exam.”
“We put together a guidebook for teachers and a companion guidebook for learners to help students learn to pay attention to the discriminating features that distinguish various diagnoses,” Dr. Yudkowsky said. “Experienced clinicians do this automatically, but students don't. What we're trying to do is encourage them to start thinking while in the room with the patient — to have their hypotheses drive, to some extent, what they're doing.”
Kamel H, Dhaliwal G, Josephson A, et al. A randomized trial of hypothesis-driven versus screening neurological examination. Neurology
2011; E-pub 2011 Sept. 7.
©2011 American Academy of Neurology
Yudkowsky R, Otaki J, Bordage G, et al. A hypothesis-driven physical examination learning and assessment procedure for medical students: initial validity evidence. Medical Education
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