Originally published in IMpact (Summer 1995), a publication of the American College of Physicians. Reprinted with permission.
As medical schools struggle to find new ways to present an ever-growing body of knowledge to a diverse group of students, problem-based learning (PBL) curricula are rapidly establishing a niche as an alternative to the traditional lecture-based course format. With names such as New Pathway, Parallel Curriculum and Integrated Learning Track, PBL programs might appear to be just another collection of acronyms in the alphabet soup of medical education. However, PBL programs represent a major departure from conventional lectures and multiple-choice exams, and they are gaining momentum nationwide.
Almost all medical students have had some experience with problem-solving exercises based on patient case histories, but designing an entire medical school curriculum around such exercises is quite a different matter. The first problem-based learning curriculum in North America was adopted at McMaster University in Ontario, in 1969. In the United States, the University of New Mexico was the first to adopt a PBL curriculum, in 1979 (1). Today, PBL curricula are in use at numerous medical schools across the United States. PBL programs seek to integrate basic science and clinical knowledge, improve problem-solving abilities and enhance patient examination and diagnosis skills.
The PBL curricula vary from school to school but certain key elements are common. Unlike traditional curricula based on large-group lectures, PBL programs are built around small, interactive groups. One or two faculty tutors, often a basic scientist and a clinician, oversee the group. The role of the tutors is to facilitate the discussion, but not to teach the subject matter. The group is presented with a patient case, and the students then identify learning issues related to the case. Students then research these learning issues and present what they have learned to their classmates. Vigorous discussion and critical analysis are encouraged. Unlike traditional lectures, in which students passively receive information from professors, PBL students must actively seek answers to their questions from literature and other sources.
Instead of learning subject matter sequentially and by discipline, students in PBL programs learn material in the context of a patient case. For example, a case involving a patient with lung disease might raise learning issues concerning anatomy and histology of the lungs, respiratory and acid-base physiology, neural control of breathing, lung pathology and physical examination of the chest. PBL proponents believe that learning these topics in a patient-based context makes them seem more relevant to students and improves retention. "If you're learning the Krebs cycle while taking care of a patient with diabetes, it sticks," notes University of Texas Medical Branch at Galveston professor Michael Ainsworth, M.D., who helped develop a PBL program at UTMB.
The selection of specific biomedical topics covered may at first appear to be random and haphazard compared to the orderly, encyclopedic treatment of each major discipline in a traditional curriculum. However, over the course of two or more years, a properly designed PBL program can include all of the topics covered in a traditional program, a fact supported by one study which found no statistically significant difference between the NBME Part I scores of Harvard Medical School's New Pathway students versus traditional-curriculum students at the same school (2).
In PBL programs, attendance and participation at small-group sessions are essential. Students must come to the sessions prepared to present, discuss and defend the information they have gathered. In many PBL programs, both tutors and peers grade students on group participation and preparation. Traditional curricula, in contrast, rely primarily on non-interactive lectures which many students do not even attend, and most students do not study the lecture material until after the lecture (1).
The medical library is a key component of a PBL curriculum. In a traditional curriculum, students often depend on assigned textbooks, handouts from professors, and student-generated lecture notes. The latter two sources are particularly prone to being outdated, incomplete or inaccurate. PBL students usually do not have assigned texts and utilize a wide variety of resources such as texts, monographs, journals and computer resources. PBL students use library resources five to ten times more than traditional-curriculum students (3). Students commonly encounter conflicting information which must be addressed by group discussion (1). PBL advocates view this as a strength of the program, as it encourages critical thinking and the need to use current sources for rapidly changing areas of scientific knowledge. It also helps students view issues from a variety of perspectives.
Proponents of PBL programs claim that the independent learning skills and extensive use of medical literature give students excellent training in the skills of lifelong learning required for the practice of medicine in the modern era. Essentially, the PBL concept strives to teach students medicine the same way they will practice medicine, that is, in the context of individual patients, with reference to current literature and consultation with colleagues. A study of Harvard medical students found that the New Pathway students learned in a more reflective manner and memorized less that than their counterparts in a traditional program (2). Similarly, graduates of the PBL curriculum at McMaster University were found to be more up to date in knowledge of the management of hypertension than a control group of traditional-curriculum graduates (4).
In traditional programs, lectures are usually given by professors with expertise on the topic being taught. It is much more difficult to assign "content experts" to PBL groups, due to the wide variety of learning issues covered in each case as well as the larger number of professors needed to accommodate the smaller student-to-faculty ratio. Traditionally, tutors have been expected to have more expertise in small-group facilitation than in subject areas. However, studies of expert-led and non-expert-led PBL groups have shown that groups with expert tutors identified more learning issues, and these were much more congruent with the case's intended learning objectives (5). Expert-led groups also reported higher levels of satisfaction and higher examination scores. An important challenge to schools using a PBL curriculum is to prepare tutors in both small group facilitation as well as the content of the case, since it is unlikely that a sufficient number of content experts for any given case would be available at most institutions (6).
The PBL philosophy also shakes up conventional ideas about testing and grading. The UTMB program, for example, does away with multiple-choice exams, replacing them with essay and oral examinations. "Grades based on multiple-choice exams only give you a narrow view of what the student's abilities are," explains Payer. "[The new exams] are designed to give students the ability to explain how they know something and elaborate on it." Similarly, the PBL program at Bowman Gray School of Medicine relies on essay questions, an oral examination and limited use of multiple-choice questions (3). Both schools also assess the student's history-taking and physical examination skills with standardized patient examinations at regular intervals.
PBL programs are not without disadvantages. Students may become frustrated by the apparent lack of structure. Trivial topics can sidetrack group discussions. Interpersonal conflicts may impair the group's effectiveness. As with any group project, a small number of students may do a disproportionate amount of the group's work. It is the responsibility of the group members as well as the tutors to identify these problems when they arise, a situation which may place students in the uncomfortable position of having to point a finger at a fellow student. In addition, the lower student-to-faculty ratio of PBL programs requires more faculty time and is more expensive than a traditional program. Schools with dual curricular tracks must work to prevent misunderstandings between PBL and non-PBL students, as students in the traditional program may feel that the PBL students receive preferential treatment and more individual attention.
Are traditional curricula destined to become a relic of medical history? Probably not. The majority of schools using PBL curricula use it as an alternative track for selected students and have no intention of abandoning the traditional program. "Neither of the two is the better curriculum," states Andrew Payer, Ph.D., a UTMB professor who has spent several years developing the school's PBL program. "Some students will learn better in the PBL environment. We don't expect it to be right for everybody." Perhaps, then, the most significant change instituted by PBL programs lies not in the PBL concept itself, but in the idea that no single curriculum is best for all students--an idea that is particularly relevant at a time when the demographics of medical school student bodies are moving toward greater diversity. The curriculum of the future may actually be multiple curricula designed to meet the individual needs of different students.
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