Problem-based learning (PBL) is an approach to medical education in which students learn collaboratively by confronting clinical problems. Courses are usually organised thematically rather than by discipline, often by a small team of teachers with different disciplinary backgrounds.

The group problem-analysis and independent self-directed study -- rather than teacher- or examination-driven education -- in PBL may encourage students to become more thoughtful problem-solvers and life-long learners.¹

PBL is now the instructional method of choice in an increasing number of medical schools around the globe. Introduced in 1969 at McMaster Faculty of Health Sciences, Canada, PBL is now used in about 150 (of 1400) medical schools worldwide.² In Australia, PBL was introduced quite early, in 1978, through the pioneering efforts of the late David Maddison and staff at the University of Newcastle. Other medical schools in Australia, such as the University of Sydney, Flinders University of South Australia, the University of Queensland and Monash University, have since followed.

Why has PBL recently become popular in medical education? Clearly, the approach matches current efforts to involve students more actively in their own education, which does improve learning.³ In addition, students prefer PBL to other methods and spend more time on self-directed learning activities, using more information resources.⁴ In this issue of the Journal Finucane et al discuss these and other issues in PBL.⁵

Do students trained through PBL become better doctors? This question is not easy to answer, partly because there are few comparative studies of actual behaviour in professional practice and partly because it is difficult to attribute differences (or their lack) to specific features of the curricula being compared.

In a recent study, final-year medical students from Maastricht University (which has a PBL-based curriculum) had a much higher level of proficiency in most of the professional skills tested than students from another Dutch medical school with a conventional curriculum.⁶ But is this effect attributable to the Maastricht PBL curriculum, or is it the result of the more extensive skills training also provided by that curriculum?

Another possible confounding factor is that admission policies in some medical schools with PBL differ from those of conventional medical schools; the fact that students have different characteristics to begin with may itself explain differences in knowledge and skills shown both during the course and after graduation.

With these reservations in mind, I will summarise what is known about the impact of PBL curricula on students, confining myself to studies that compared graduates or final-year students from medical schools with conventional, lecture-based programs and schools with PBL programs.

Do students from PBL institutions become life-long learners? Some believe that PBL encourages the acquisition of independent study skills. Such skills would help a practitioner to keep up-to-date. Primary care physicians who graduated from McMaster University displayed more up-to-date knowledge of an important clinical concept (hypertension),⁷ but graduates from the same institution did not participate in more continuing education activities.⁸

Are there any differences in practice patterns? Studies in the United States⁹ and Finland¹⁰ have shown that graduates from schools with innovative curricula are more likely to choose a career in primary care than their counterparts from more traditional schools; these students also report their education to be more relevant to their present practice. These findings have not been replicated in other countries. It seems that career choice is more a matter of the explicitly stated mission of a school than its instructional approach. However, McMaster graduates in general practice, compared with matched controls from other Ontario medical schools, billed the healthcare system less, had fewer patients and spent more time with them, and referred less to psychotherapeutic services, suggesting that they were more comfortable with providing the services themselves.¹¹

Are there differences in medical knowledge? In the US, the source of most of these comparisons, graduates from PBL schools acquire less knowledge of the basic sciences, but compensate with slightly more clinical knowledge.¹² Overall, there are no differences in medical knowledge; PBL is just as good (or poor) in this respect as conventional medical education.¹³

Does PBL increase diagnostic competence? Small-scale studies have had mixed results. Patel et al asked 54 students from two medical schools -- one with a PBL-based curriculum and the other conventional -- to diagnose a clinical case and explain their diagnosis, and then examined their reasoning processes. The PBL students explained the causes more extensively, using the relevant biomedical knowledge, but made more diagnostic errors.¹⁴ Other investigators, using a similar task, found that PBL students also showed more extensive causal reasoning, but made fewer diagnostic errors.^15,16

As these studies presented only one or two cases to be solved, the findings may reflect the specific cases rather than resulting from the instructional formats compared. In a large-scale study, in which 612 students were presented with 30 epidemiologically representative cases and provided a diagnosis for each of them,¹⁷ Maastricht final-year students¹⁷ performed better than the group from the medical school with the conventional curriculum, with the mean difference between the two groups being 1.5 cases out of 30.

If we extrapolate these findings to actual practice (under the perhaps questionable assumptions that these students, in the future, will actually see about 30 patients per day, and that these paper-and-pencil test findings do signify a difference in actual diagnostic expertise between students from the two schools), the results imply that for each month (20 working days) in practice a graduate from the conventional medical school would miss 20 x 1.5 cases (ie, about 30 diagnoses) that would be accurately made by a Maastricht graduate. These findings suggest that even relatively small effects of curriculum type, when extrapolated, may affect the quality of everyday diagnostic performance in non-trivial ways.

There is some evidence that PBL at least contributes to the making of better doctors. The evidence, though scarce, seems to suggest that students trained through the confrontation with clinical problems become more accomplished diagnosticians. In addition, after these students graduate, they appear to have better self-directed learning and other professionally relevant skills. Much more research, of course, is mandatory. This will be an interesting challenge for the new Australian PBL medical curricula.

Henk G Schmidt
Professor of Psychology and Health Professions Education
Faculty of Psychology, Maastricht University, the Netherlands

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