Gastroenterology and Hepatology


William Rosenberg MA MBBS DPhil MRCP

Introduction to evidence-based gastroenterology and hepatology

In this essay I will present a working definition of evidence based medicine, discuss the ways in which it differs from traditional approaches to clinical practice: suggest some benefits for gastroenterologists and hepatologists and highlight some of the particular challenges that it presents to us.

Evidence based medicine is the explicit and judicious use of current best evidence and clinical expertise in making decisions about the care of patients. As such it requires the integration of individual clinical expertise and acumen with the best available external evidence and with our patients’ values and preferences. By individual clinical expertise we mean the increasing proficiency acquired through clinical experience, reflected in more effective and efficient clinical decision making, and the ability to accommodate patients’ rights needs and preferences when making decisions about their care. When using the term “best available external evidence” we refer to clinically relevant research that often comes from the basic sciences such as immunology, physiology and molecular biology, but especially from patient-centred clinical research into the accuracy and precision of diagnostic tests, the predictive power of prognostic markers, and the efficacy and safety of therapies. Throughout we aim to recall that the research method should be determined by the question so that while an RCT is the appropriate methodology to investigate the efficacy of a therapy, a prospective cohort study (and not an RCT) will provide the best evidence about prognosis.

When considering evidence we must bear in mind that today’s certainties are tomorrows bad practice! External clinical evidence has a short doubling-time. It both invalidates previously accepted tests and treatments and replaces them with new ones that are more powerful, more accurate, more efficacious, and safer, for the moment! So we must attempt to keep up to date. In advocating the integration of clinical expertise and external evidence we argue that neither alone is enough. Without the former, practice risks becoming evidence-tyrannised, for even excellent external evidence may be inapplicable or inappropriate for an individual patient. Without the latter, practice risks becoming rapidly out of date, to the detriment of patients and patient-care.

When applying this process in the care of patients it is of prime importance that we acknowledge the rights, needs and preferences of patients. This requires that we not only maintain an awareness of the evidence, but that we understand it sufficiently well to be able to explain it to our patients in a variety of different ways. Acquiring the skills to communicate effectively with a broad range of patients thus becomes one of the core competencies of EBM. This is likely to involve mastery of verbal, numerical and visual methods of communicating risks, benefits and consequences and may be augmented by many of the novel biostatistical techniques developed by practitioners of EBM such as Numbers Needed to Treat or Harm, Likelihood Ratios and Odds ratios.

Many thoughtful and experienced traditional physicians have asked what is the difference between these precepts that we have labeled “EBM” and traditional best practice? At first glance this is a valid question. In answer we identify five areas in which EBM differs from prior models.

  • First, in many of the conceptual ways in which EBM addresses clinical practice, such as explicit question formulation, EBM differs from traditional approaches. We have found that many of the difficulties that students and qualified clinicians experience when trying to find evidence relate to problems with defining a clear, searchable, answerable and relevant question. Emphasising the process of explicitly formulating such a question represents a conceptual advance of EBM.
  • Secondly, EBM has introduced a number of strategies into the practice of medicine that have improved access to evidence, and the evaluation, integration into clinical care and dissemination of this evidence. These include the development of optimal strategies for searching electronic databases, “users’ guides” to critical appraisal, biostatistical methods of expressing the impact of evidence (such as NNT) and dissemination of evidence through sources of secondary publication such as ACP Journal Club and Evidence Based Medicine.
  • Thirdly, EBM encompasses interpreting and appraising advances in research methodologies such as the use of systematic reviews and meta-analyses.
  • Fourth, are the new ways of presenting the results of research in numerical form such as NNT,LR, OR and NNH that have developed from biostatistics. These ways of presenting data provide new ways of viewing results and some can be used to enhance communication with patients and colleagues.
  • Finally, EBM provides an integrated system for promoting patient problem based, self-directed learning which can be fully integrated into service delivery, meeting the competing demands of training and patient care.

Thus EBM is an approach to clinical problem solving, a means of determining rational practice, a method of integrating service with training and education, a way of generating research ideas and, in summary, Best practice made EXPLICIT and ACCESSIBLE. In contrast it is specifically not just what we’ve always been doing, or cook-book medicine and it is not only about RCTs & meta-analyses. Although these research methods have their place, they are inappropriate ways of studying some questions. EBM does not lead to rationing or cost-cutting except where costly practices are ineffective. Indeed evidence-based practices may be costly as in the case of adding ribavirin to interferon in the treatment of chronic hepatitis C. Finally because EBM requires the integration of individual expertise with the best available external evidence, EBM is not disrespectful of experience, rather it values experience.

Practising EBM in isolation tends to be lonely and is likely to be inefficient. Forming a team with colleagues is, in our experience rewarding and pleasurable. Expertise can be shared and tasks distributed. Participants at different stages of training may work together to mutual benefit and the shared practice of EBM can make powerful contributions to team building. Multidisciplinary groups can practise EBM together with great success. In our experience, differences in experience, background and perspective can require skill in facilitation but the benefit of recognising different perspectives on common shared problems can be enormous. Most groups will encompass members who bring specific expertise but any skills not shared within the group can be sought outside and learnt. We have enjoyed and benefited greatly from training in searching and library skills by librarians. By contrast we have rarely had to request help from statisticians, finding that esoteric statistical tests are a reliable surrogate marker for low impact research findings.

Much of the pioneering work in EBM has centred on questions and research in cardiology. EBM poses slightly different challenges to gastroenterologists and hepatologists and consideration of these differences is instructive. By contrast with cardiologists we use a wider range of diagnostic tests and we tend to work with colleagues from many different disciplines such as psychopathology, biochemistry, radiology and surgery. We have had to rely on the results of many small trials of therapy, partly because of the lower prevalence of many gastroenterological and hepatological diseases and partly because we have been slower to embrace “mega trial” methodology. In contrast with the acute interventional cardiologist, we tend to spend more time managing patients with chronic relapsing conditions such as inflammatory bowel disease and viral hepatitis. Although there are similarities in our use of interventional or procedural techniques, many of those used in gastroenterology are more operator dependent than those used by cardiologists. These contrasts both explain some of the differences in quality and quantity of EBM resources between gastroenterology and cardiology but also highlight some of the challenges that face us, all of which may be easily addressed. As gastroenterologists and hepatologists there is much we can take from EBM and there are many ways in which we can use it to our benefit. When confronted by clinical problems the strategy of question formulation can be used to reduce complex clinical scenarios into an array of addressable questions that can then be prioritised in a hierarchy of importance. We advocate placing common questions asked by patients and physicians at the top, followed by common problems asked by us, less common problems of interest to patients and ourselves and finally rare questions of interest to us alone.

We try to make optimal use of information technology, learning the most successful searching strategies for the best databases and taking note of useful websites such as ScHARR and HEPNET. [no longer on-line]

In a discipline so reliant on interdisciplinary working, we have found that mastering the skills of critical appraisal has greatly enhanced our ability to contribute to debates about practice outside our individual areas of expertise but within the specialty. Thus a meeting between physicians, surgeons and radiologists about the management of hepatic tumours involved each group using a common strategy for critically appraising the evidence in order to reach consensus.

It would be very wrong to ignore the considerable achievements that have already been attained in evidence-based gastroenterology and hepatology. Important systematic reviews have changed perspectives and practice in the areas of therapy for primary biliary cirrhosis1, inflammatory bowel diseases2 and hepatitis C3. There are many examples of new initiatives in which gastroenterologists are working together to answer big questions with large multicenter trials addressing the use of new therapies in IBD, colorectal cancer diagnosis and the use of serological markers of liver fibrosis. The success of various Cochrane groupings within the field provides further evidence of the growing recognition within the speciality of the power of EBM approaches to clinical research.

In the sphere of clinical excellence recent years have witnessed the proliferation of valid practice guidelines and studies designed to generate the evidence that underpins them such as the BSG gastrointestinal bleeding. The challenges that lie ahead are the application of good quality clinical research into the effectiveness of the treatments and diagnostic tests that we use; promotion of EBM in the primary sources of publication and the development of EB secondary sources of publication. EB workshops within the specialty would be exciting. New publications are in preparation and there is undoubtedly the need and demand for an evidence based gastroenterology and hepatology journal.

In summary the benefits of EBM to us as gastroenterologists and heptologists are to ourselves, our patients and the health care systems in which we work. For ourselves, EBM provides a means for keeping up to date and maintaining our clinical independence. Our patients should benefit as a result of us being as well informed and contemporary as possible and the process of EBM should ensure that we take account of their needs and wishes when integrating external evidence with their individual cases. We may become better at finding more comprehensible ways of sharing evidence with our patients by adopting some of the EBM methods of expressing the results of research. Healthcare systems such as the NHS benefit from EBM by providing a structure in which we can easily and efficiently integrate education with service delivery. Health economic issues can be resolved using EBM to justify the elimination of ineffective and costly practises to release resources better used in effective practices. EBM should also meet some of the needs of quality assurance by promoting the more uniform delivery of “best practice.”

Other resources for evidence-based gastroenterology and hepatology

  • [no longer online]


  1. Simko-V; Michael-S; Prego-V. Ursodeoxycholic therapy in chronic liver disease: a meta-analysis in primary biliary cirrhosis and in chronic hepatitis. Am-J-Gastroenterol. 1994 Mar; 89(3): 392-8 
  2. Pearson DC, May GR, Fick G, Sutherland LR. Azathioprine for maintaining remission of Crohn’s disease (Cochrane Review). In: The Cochrane Library, Issue 1, 1999. Oxford: Update Software. 
  3. Poynard, T., Leroy, V., Cohard, M., Thevenot, T., Mathurin, P., Opolon, P., and Zarski, J.P. Meta-analysis of interferon randomized trials in the treatment of viral hepatitis C: effects of dose and duration. .Hepatology 24(4):778-789, 1996.