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Evidence-based Radiology Series |
1 From the Department of Radiology, St Vincent's University Hospital, Elm Park, Dublin 4, Ireland (D.E.M.); and Department of Medical Imaging, Toronto General Hospital, Toronto, Ontario, Canada (M.S.). Received January 3, 2006; revision requested March 2; revision received April 13; final version accepted June 12. Address correspondence to D.E.M. (e-mail: dmalone{at}ucd.ie).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONSTEP 5: EVALUATECAVEATS AND COMMON QUESTIONSBOTTOM-UP EBP: EIGHT FREQUENTLY...References |
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© RSNA, 2007
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONSTEP 5: EVALUATECAVEATS AND COMMON QUESTIONSBOTTOM-UP EBP: EIGHT FREQUENTLY...References |
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STEP 5: EVALUATE |
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TOPABSTRACTINTRODUCTIONSTEP 5: EVALUATECAVEATS AND COMMON QUESTIONSBOTTOM-UP EBP: EIGHT FREQUENTLY...References |
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Self-Evaluation
The Web site of the Centre for Evidence-Based Medicine of the University of Toronto, Toronto, Ontario, Canada (2) gives a concise and readily available guide to the subject of self-evaluation. The authors of this Web site consider what questions need to be asked for self-evaluation in (a) asking answerable questions, (b) finding the best external evidence, (c) critically appraising the evidence for its validity and potential usefulness, (d) integrating the critical appraisal with clinical expertise, (e) and applying the result in clinical practice. They also consider self-evaluation in teaching evidence-based medicine (EBM) and integrating it into continuing professional development (2). The principles of self-evaluation are readily transferable to radiology. The questions created by the authors of this Web site are clear, simple, and easily understood. An example of their questions for "self-evaluation in integrating EBM critical appraisal with clinical expertise and applying the result in clinical practice" is shown in Figure 1.
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Conclusive evidence.—If the evidence is conclusive, a change in local practice may be indicated. This change should, ideally, be followed by collection of data to evaluate whether the anticipated effect is occurring. The process of establishing best practice, implementing necessary local changes, evaluating their effects, and making further modifications as indicated is termed an "audit cycle" (3). Thus, bottom-up EBP can contribute to audit and practice development processes, helping to turn "gray areas" of local practice into strong areas managed by evidence-based protocols and/or guidelines. The Web site of GIMBE (Gruppo Italiano per la Medicina Basata sulle Evidenze), the Italian EBM group, can be recommended to interested readers (4). This Web site has an audit page that contains many links to useful audit publications, organizations, databases, and software, as well as a link to one of the articles in the "User's Guides to the Medical Literature" series in the Journal of the American Medical Association that considers the critical appraisal of articles about clinical utilization review (5). The current and potential relationships between bottom-up EBR and radiology education will be discussed in detail in a later article in this series.
Inconclusive evidence.—On the other hand, if the evidence is inconclusive, it may be clear where the gaps are in the current literature. A single-center or multicenter research project can be undertaken to address them. As resources for the publication and dissemination of evidence-based information and ongoing multicenter trials within radiology evolve (an issue that will be considered briefly later in this article and also later in the series), it is anticipated that the number of times that bottom-up EBP yields inconclusive results will decrease. When the current best evidence is inconclusive, clinical expertise guides interim decisions about departmental policy and the literature should be reviewed at intervals.
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CAVEATS AND COMMON QUESTIONS |
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TOPABSTRACTINTRODUCTIONSTEP 5: EVALUATECAVEATS AND COMMON QUESTIONSBOTTOM-UP EBP: EIGHT FREQUENTLY...References |
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It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness, it was the epoch of belief, it was the epoch of incredulity, it was the season of Light, it was the season of Darkness, it was the spring of hope, it was the winter of despair, we had everything before us, we had nothing before us, we were all going direct to heaven, we were all doing direct the other way—in short, the period was ... like the present period...
Charles Dickens, A Tale of Two Cities (6)
Caveat emptor (let the buyer beware).
Anonymous, Ancient Rome
EBP has its supporters and its detractors. What do you mean when you say EBP? There are several different schools of thought that define themselves as "evidence-based"; for the purposes of this article, they will be considered as bottom-up and top-down schools of thought. This concept helps the EBP user to separate different paradigms conceptually. Top-down schools of thought exist, such as Agency for Healthcare Research and Quality (AHRQ) institutions (7), centralized expert panels, and public health schools of EBP. The bottom-up approach is the McMaster-CEBM paradigm.
Top-down EBP
AHRQ institutions.—In 1997 the Agency for Healthcare Policy and Research, now known as the AHRQ, launched its initiative to promote EBP in everyday care through the establishment of 12 EBP centers. The EBP centers develop evidence reports and technology assessments on topics relevant to clinical, social science/behavioral, economic, and other health care organization and delivery issues—specifically those that are common, expensive, and/or significant for the Medicare and Medicaid populations (7). With this program, the AHRQ became a "science partner" with private and public organizations in their efforts to improve the quality, effectiveness, and appropriateness of health care by synthesizing the evidence and facilitating the translation of evidence-based research findings. In June 2002, the AHRQ announced the second award of 5-year contracts for EBP centers (EPC II) to 13 centers to continue and expand the work performed by the original group of EBP centers. These North American centers (three are Canadian) will produce evidence reports and technology assessments to support guideline development by other groups (7,8). The centers are charged with supporting research designed to improve the quality of health care, reduce its cost, address patient safety and medical errors, and broaden access to essential services.
For AHRQ institutions of EBP: (a) Research evidence will be high quality, but methods and evaluation are not necessarily either transparent or reproducible. (b) Clinical expertise will be strongly represented. (c) Patient values are very likely to be considered at the cost-effectiveness level, but are not, to our knowledge, specifically targeted.
Summary: The literature searches are extensive and are performed by National Library of Medicine staff. This is definitely an evidence-based resource. The overall number of topics addressed is relatively small, and the frequency of updates is difficult to establish (eg, uterine artery fibroid embolization evidence is dated 2001). Because of a lack of explicitness about methods, there is a risk that this policy may result in the institutionalization of the concept of "eminence-based practice" (9), from which EBP is meant to be an evolution (10). The results of eminence-based assessment are typically variable (11,12).
Centralized expert panels.—This school of thought, which is largely based in the educational organizations of Great Britain and North America, has long recognized that practitioners seek evidence when clinical decisions cannot be made with confidence and has attempted to fill the evidence void with accessible, problem-based guidelines derived from: (a) comprehensive literature searches (eg, MEDLINE) and (b) an evidence base of effectiveness that includes specialized expert analyses of evidence and the consensus agreement of experts.
For the centralized expert panels school of EBP: (a) In regard to research evidence, this group accepts that, for radiologists, there is little evidence about the effects of diagnostic imaging on outcome, and this group grades the evidence base for individual problems (13–16). (b) Clinical expertise is represented among the constituents of expert panels. Panel selection criteria are relatively opaque. (c) Patient values are very likely to be considered, as panel membership is typically broad and multidisciplinary.
Summary: The recommendations of these centralized expert panels are definitely evidence-based because of the very comprehensive literature search these organizations perform. Nevertheless, once the evidence has been collected, unless a consensus panel uses very explicit appraisal methods, the final results may be similar to the eminence-based practice paradigm (9), which has historically produced variable results (11,12).
Public health EBP.—The economic community is not especially sympathetic to demands for increased medical funding. Rich countries everywhere are struggling to finance health care. Across the developed world, health budgets are feeling the strain. None of the health models clearly has an advantage in "keeping a lid" on health spending. Health spending inexorably rises because of expensive advances in medical technology in a marketplace in which providers are particularly powerful, since physicians determine what medical care is necessary. Economists believe that, instead of yearning for new sources of extra revenue after years of bumper budgets, physicians should accept that securing better value for money must be the priority (17). A requirement for a high level of evidence can be inserted as a "gatekeeper" for funding. While it is appropriate to evaluate the efficacy of medical interventions, there is an inherent philosophical conflict between this school of thought and that of the original EBM workers. Physicians practicing McMaster-CEBM EBP will identify and apply the most efficacious interventions to maximize the quality and quantity of life for individual patients; this may raise rather than lower the cost of their care (18).
For public health EBP: (a) Research evidence may be of very high quality because programs may be initiated or funded at the governmental level (7,16). (b) Clinical expertise will not necessarily be involved in high-level decision making in every country. (c) In regard to patient values, an individual patient's problem may be disregarded or devalued for the greater good.
Summary: Multiple stakeholders now seek to assume the EBM mantle for purposes that often contradict its original intent. Managers, equating lack of evidence with lack of effectiveness, use EBM as a rationale for cutting services. Industry generates evidence of questionable quality to promote its products. EBM, developed as a means of taming the unscientific and messy world of clinical practice, has itself entered the unscientific and messy world of politics (19). Administrators and fundholders may perceive an anarchic medical profession spending their money in a profligate and unnecessary manner. EBP may be seen as a means to shackle physicians. EBP practitioners must take care that they are not used as dupes in a political game of health economics (20). Options for practitioners encountering weak evidence will be discussed further below.
Bottom-up EBP: The McMaster-CEBM Paradigm
The bottom-up concept of EBP began in 1996 with David Sackett, who wrote, "Evidence-based medicine is not ‘cookbook’ medicine. Because it requires a bottom-up approach that integrates the best external evidence with individual clinical expertise and patients' choice, it cannot result in slavish, cookbook approaches to individual patient care... Clinicians who fear top-down cookbooks will find the advocates of evidence-based medicine joining them at the barricades" (18).
The original EBM definition includes the integration of three dimensions: best research evidence, clinical expertise, and patient values in patient care (18,21). While core epidemiologic concepts include standardized critical appraisal methods and a hierarchy of evidence, individual clinical judgment (ie, the proficiency and judgment that individual clinicians acquire through clinical experience and clinical practice [18]) and patient values are clearly flagged as essential components of this paradigm. This is a very important concept, because otherwise the administrators, business people, and allied health professionals (eg, nurse specialists) may be handed a "flat" medical environment in which the judgment of the medical specialist and the pleas of the sick for treatment count for little in the absence of conclusive evidence, and all professional opinions carry equal weight when the available evidence is weak. The first four articles in this series (22–25) have explained the McMaster-CEBM concept in detail and have explored how it can be applied to problems arising in the practice of radiology.
Appraisal of the McMaster-CEBM Paradigm
Having described various EBP philosophies, we will now concentrate on the pros and cons of the McMaster-CEBM school of thought.
Champions versus critics: Bottom-up EBP has its supporters and its detractors. The contrasting viewpoints (Fig 2) have been largely summarized by Trinder (26). The final point in Figure 2 appears especially important in the hospital workplace. That is, the convergence of essentially different disciplines can lead to tensions between the allied health professionals of nursing, physiotherapy, and medical practitioners if proficiency in searching the literature and appraising retrieved material is overvalued and the necessary, traditionally acquired clinical expertise of the original EBM definition (be it medical, surgical, radiologic, or nursing expertise) is devalued or ignored. Without clinical expertise, practice risks becoming tyrannized by evidence, for even excellent external evidence may be inapplicable to or inappropriate for an individual patient (18).
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BOTTOM-UP EBP: EIGHT FREQUENTLY ASKED QUESTIONS AND BEST CURRENT ANSWERS |
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TOPABSTRACTINTRODUCTIONSTEP 5: EVALUATECAVEATS AND COMMON QUESTIONSBOTTOM-UP EBP: EIGHT FREQUENTLY...References |
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The implication that physicians must always seek external evidence seriously undermines the effort of promoting the appropriate use of evidence (1).
Question 2: What If I Search and There Is No Evidence?
So what? In clinical practice, doctors and patients are rarely unhappy when situations turn out well and the patient recovers. Medicolegal problems arise for radiologists because of many reasons, including the problems of inappropriate examinations and incorrect interpretations. If a radiologist is aware of a knowledge gap, he or she may be cautious or uncertain. If a radiologic decision is made in conditions of some uncertainty and is subsequently judged to be incorrect on the basis of recent publications, the medicolegal position of the radiologist is insecure. Competence in online literature searching and rapid critical appraisal is protective in this context, even if no new or strong evidence is identified. Knowing that there is no readily available recent evidence or interval change in conventional wisdom is very reassuring in situations where major management changes rest on the radiologic advice and interpretation. Anecdotally, using EBP methodology can also identify the even more dangerous knowledge gaps—those we were unaware of until we performed the literature search!
Question 3: What If the Evidence Is Weak?
In this situation, the response depends on the EBP paradigm from which the practitioner is working. Pure adherents of the top-down AHRQ institutions and centralized expert panels schools of thought may search for guidance within the guidelines, and if only weak evidence is available, they wait for the next edition of the guideline. Pure adherents of the public health EBP school will recommend no action, because there is no conclusive evidence. Users of the McMaster-CEBM paradigm will weigh up the best current evidence in the context of their clinical expertise and patient values before making a decision. They may decide either to act or to wait for better evidence. Good physicians use both individual clinical expertise and the best available external evidence, and neither alone is enough (18).
Question 4: Should We Act on Weak Evidence?
This question follows naturally from the preceding question. Philosophically, it means that we must consider the difference between evidence and judgment. This may, perhaps, be best illustrated by a short clinical example from an interesting essay (27). In early 1983, the viral cause of acquired immunodeficiency syndrome, AIDS, was not yet documented. Despite this, experts, using an analogy with hepatitis B, declared that the probability of an infectious cause was high and that there should be keen awareness of blood product–associated cases (28). The only evidence for blood transmission available at the beginning of 1983 consisted of isolated reports involving patients who had received blood products and could have secondarily developed the disease (29–31). This led to the statement that the available medical and scientific evidence that AIDS could be spread in blood components was incomplete (32). On the basis of incomplete evidence, measures were taken by U.S. blood banks to screen blood from high-risk groups (32). At the same time in Canada, the Red Cross considered that the probability of developing AIDS after blood transfusion was low, which was true, and a less aggressive approach was taken to screen blood. In 1997, the Commission of Inquiry on the Blood System in Canada concluded that the Red Cross should not have required "conclusive evidence" before taking action to reduce the risk of AIDS (32).
In certain circumstances, it may be a matter of what difference we believe the evidence can make that will result in us accepting to act on it (27). The author, Auclair (27), goes on to say that "evidence confers subjective probability to a hypothesis based on assessments of differences (for example, risks vs benefits)." The assessment of differences is the domain of judgment. Judgment in medicine is the ability to perceive differences, the ability to discriminate between a banal observation and a significant one, the ability to perceive degrees, and the ability to estimate the degree of coherence of a set of theses. If we want to improve how we practice medicine, we have to improve our ability to judge. Practice in decision analysis and assessment of probabilities is a start. There may be no shortcuts, however, to the acquiring of sound clinical judgment; perhaps "judgment is the understanding that comes with age" (33). All adherents of the public health school of EBP should read the article by Auclair (27). Internationally, the blood transfusion service–AIDS scenario has shown that citing lack of evidence as a reason for inaction will not necessarily always excuse the health care provider if the stakes are high and the wrong decision is made.
This philosophy is completely in accordance with the McMaster-CEBM philosophy of EBP (18,21), with its inseparable triad of best current evidence (determined explicitly and reproducibly), clinical expertise, and patient values. External clinical evidence can inform, but can never replace, individual clinical expertise, and it is this expertise that determines whether the external evidence applies to the individual patient at all and, if so, how it should be integrated into a clinical decision (18).
In one of the first Radiology publications on EBP, Wood (10) noted that the eminence-based medicine paradigm evolved in an era when all evidence was weak. The measure of authority was proportional to the weight of individual experience. Medical decisions depended on a thorough knowledge of pathophysiology and on thoughtfully acquired clinical judgment (9). Given the variable results of the eminence-based paradigm, it is unlikely that it will ever again be acceptable to administrators, fundholders, or the public for a medical expert to pronounce on issues "ex cathedra" without having first performed an evidence-based analysis of the subject in question. Nevertheless, it is suggested that to discard this paradigm completely would be to "throw out the baby with the bath water," and the final place of EBP vis-a-vis traditional practice methods will most likely be as an additional tool within existing practice (10,26).
It is clear from the above that it will sometimes be essential to act on weak evidence. In these cases, it will be necessary for properly informed medical experts to make decisions on the basis of the balance between factors such as the degree of illness of the patient or patient group, the cost of the imaging method or intervention, its associated toxicity or risk, and the rarity of the condition in question (1). Depending on circumstances, the burden of proof might rest on demonstrating efficacy or demonstrating ineffectiveness of the method and should change along the spectrum of disease. There are precedents in the legal system; where U.S. criminal law requires proof beyond a reasonable doubt, in civil cases a preponderance of evidence suffices (1). This is an area of "medical philosophy" that requires further, thoughtful, multidisciplinary development.
Question 5: Is EBR the Same as EBM?
Bottom-up EBR is, in its evolution, diverging from EBM in some ways. There are many similarities based around the challenge that all diagnostic decision making can, and indeed must, take place in the context of continuing uncertainty (1). The EBM exercise of probability revision familiarizes students with the inherent uncertainty of medical practice. Because certainty is unattainable, students learn to evaluate degrees of uncertainty and see that medical decision making is not about being sure but rather about being sure enough (1). EBR and EBM differ in several ways:
1. Consideration of the medical effects of ionizing radiation should be an integral part of EBR (34).
2. Radiologists need to consider not only individual patients but the values and preferences of referring physicians and patient groups attending the practice.
3. Additional questions that radiologists should ask when considering the validity of diagnostic performance studies have been identified (34).
4. EBM physicians use likelihood ratios and the "Fagan nomogram" to allow them to establish posttest probabilities for individual patients (35). Anecdotally, our group has found that graphs of conditional probability (GCPs), which allow the posttest probability of positive and negative tests to be established for the whole range of pretest probabilities, are more useful to assist us, as radiologists, to guide consultations with referring physicians about the appropriateness of, and the interpretation of findings from, imaging tests (23,34,36,37).
These factors mean that the evidence-based radiologist may disagree with the evidence-based physician's choice of examination or conclusions about the value of an examination. Consider two examples:
Choice of examination: EBM versus EBR.—In a chapter on the appraisal of diagnostic test literature in a leading EBM textbook, a clinical scenario is given and an EBM approach to diagnostic test choice is described (35). In the scenario, an emergency room physician is asked to assess a 32-year-old woman with right lower quadrant pain. The differential diagnosis is appendicitis, pelvic inflammatory disease, or an ectopic pregnancy:
As you are debating whether to refer directly to surgery or to begin by obtaining a gynecologist's opinion, your colleague, an interventional radiologist, stops by on his way from performing an emergency pulmonary angiogram. You describe the patient you are attending and he mentions that up to 15% of needless laparotomies and up to 20% of admissions can be avoided if a computed tomographic (CT) scan is performed in patients like this one. He mentions ‘a very good paper that you should read, since it was published in the New England Journal of Medicine’ although the citation and the details of the investigator's methods escape him... You decide you can afford 30 minutes to look for and examine the article recommended by the radiologist.
The scenario then proceeds with the emergency room physician locating and appraising the article by using EBM methods:
Given the extreme likelihood ratios of helical CT scanning in women with abdominal pain, CT results are very likely to change management...You are sufficiently impressed by the information...that you...bypass the gynecological consultation. Your radiologic colleague facilitates an emergent scan and soon calls you back, triumphantly announcing that the results are characteristic of appendicitis. The patient is whisked to the operating room and you later hear that the patient is recovering uneventfully after the removal of her inflamed appendix.
While the EBM section of this scenario is admirable, the common set-piece of possible atypical acute appendicitis was evaluated by using EBP techniques several years ago in a study by Cunningham et al (37). These authors came to different conclusions. For a start, their answerable question (22) was, "In patients with suspected atypical acute appendicitis, how does CT compare with sonography for diagnosis?" A summary of the best current evidence at the time is shown in Figure 3, which uses GCPs to represent test performance over the whole population in question. The use of GCPs has been described in detail in other articles (23,34,36). Cunningham et al (37) had also calculated the radiation dose equivalent from their helical CT scanner as equivalent to 25–30 radiographs of the abdomen.
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The value of an examination: EBM versus EBR.—In 2003 a meta-analysis of the diagnostic performance of magnetic resonance (MR) cholangiopancreatography for suspicion of biliary disease was performed by a group comprising physicians, epidemiologists, and expert radiologists (38). In regard to common bile duct stones, the conclusion of this epidemiologically sophisticated study was that "the sensitivity of MRCP [MR cholangiopancreatography] in the detection of choledocholithiasis (0.91, 95% CI [confidence interval] 0.73, 0.97) implies that the true sensitivity for stone detection by MRCP could be in a lower range than what is commonly reported...and seems to decline with decreasing stone size" (38). They suggested that endoscopic US may be preferable to MR cholangiopancreatography in some circumstances. In considering the McMaster-CEBM process and its application to diagnostic radiology, Dodd et al (34) used the clinical scenario of suspected common bile duct stones as an example. Their conclusions were that the systematic EBR evaluation of study validity should include several questions for radiologists in addition to standard EBM questions. These are as follows:
1. Has the imaging method been described in sufficient detail for it to be reproduced in your department?
2. Have the imaging test under evaluation and the reference standard test been performed to the same level of excellence?
3. Have generations of technology development been adequately considered?
4. Has the test with the lowest radiation dose been chosen?
5. Has the radiation dose to the patient been kept as low as reasonably achievable?
6. In comparisons of CT and MR imaging, were viewing conditions comparable (film or digital images)?
Reviewing the methods section of the 2003 meta-analysis described above (38), the only technical factor taken into account was a "potential confounder"—that is, whether the MR imaging examinations were performed before or after 1996 (5 years after its introduction). This meta-analysis cannot be considered an adequate comparison of MR imaging protocols according to EBR standards. When the EBR questions were applied to this clinical scenario in the EBR article (34), two articles were appraised that had also been included in the pooled data in the 2003 meta-analysis (38). The conclusion in the EBR article was that the critical factor, radiologically, in determining the technical performance of MR cholangiopancreatography in the detection of common bile duct stones was section thickness. Imaging protocols that use a 5-mm section thickness have a much lower sensitivity than do those that use a 3-mm section thickness (34). Despite having radiologic expert advice, authors of the 2003 medical meta-analysis (38) completely missed this very important fact, which must have contributed to the reported wide confidence intervals. The limitations of eminence-based expert opinion and the issue of systematic review design have already been discussed (12,25). The conclusion from the meta-analysis will, nevertheless, influence referral patterns and practice in many centers.
These examples have implications for radiology practice. Radiologists traditionally interface with all other clinical specialties on a daily basis. The development of information technology systems, especially picture archiving and communication systems and digital dictation, have reduced the need for daily contact between hospital-based clinicians and their radiologists. In some educational cultures, radiology trainees must have clinical experience before commencing specialist training. This equips them to join clinicians in the discussion of pretest probabilities (ie, clinical information) and to work, in a level multidisciplinary team environment, as leaders and designers of the imaging activities of the team. In other educational cultures, where radiologists begin specialty training from medical school and a fee-per-item environment dictates that radiologists who "bother the clinician" looking for clinical data (pretest probabilities) are criticized, radiologists risk becoming electronically isolated interpretatively excellent "super-techs" who perform and report on the imaging tests ordered by the "real doctors." Understanding EBP principles, incorporating them into resident training in "practice-based learning" (39,40), and using them in the formal interaction between the radiology department and referring clinicians (23,24,34,36,37,41) may in the future help to reverse this trend.
Question 6: What Are the Barriers to EBP?
Resistance to change is an important barrier. Medical practitioners may be unwilling to learn EBP techniques. While many practitioners use evidence-based summaries produced by others (72%) and EBP guidelines or protocols (84%), the majority (95%) believe that learning the skills of EBM is not the most appropriate means of moving to EBP (42). Anecdotally, residents learning and presenting EBP projects may be met with skepticism, criticism, and peer pressure to perform "real research" (often descriptive case series with flawed data collection and presentation of raw data as support for exaggerated conclusions). This problem will hopefully subside as noninterpretative aspects of radiology education receive more attention in the curriculum. Those who complete EBR projects lack a place to publish, and journal peer reviewers are often unfamiliar with the concepts and methods. Low information technology and critical appraisal skills at exit from medical school, limited infrastructure, and unwieldiness of and gaps in the evidence base all artificially inflate the time needed to practice EBP (26). The issues of shortage of curricular time, lack of integration with standard radiology training, and dissemination of evidence-based information will be considered in more depth later in this series.
Question 7: Where Does EBR Fit into Academic Radiology?
Figure 4 shows a modification of the "spectrum of scholarly activities in medical practice" originally proposed by Lentle in 1994 (43). "Professionalism" approximates to the skills of bottom-up EBP. "Creative science" approximates to the skills of "technology assessment"—that is, those skills required to produce top-down secondary evidence and high-quality primary research. The relationship between the McMaster-CEBM paradigm and the technology assessment paradigm will be considered in more detail in a future article in this series. The application of explicit EBP critical appraisal methods has been discussed in detail in earlier articles in this series (23–25). EBP methods are not at present applicable to all types of radiology research. For example, only the diagnostic accuracy efficacy (diagnostic performance) and cost-effectiveness aspects of the technology assessment paradigm have been considered. Explicit critical appraisal methods do not yet exist for descriptive research, radiologic-pathologic assessment, and laboratory experiments. If explicit critical appraisal methods could be developed for purely radiologic areas of research (eg, descriptive studies) it might assist radiologists to separate generalizable from nongeneralizable results.
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This concludes the section in the Radiology series "Evidence-based Practice in Radiology" that examines the techniques of McMaster-CEBM EBP in detail and attempts to place them in an overall context, comparing and contrasting them with other EBP paradigms outside of radiology. The next set of articles will examine the potential place and impact of the McMaster-CEBM paradigm on radiology education, technology assessment, the ethics of radiology practice, and the radiology literature.
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FOOTNOTES |
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Abbreviations: AHRQ = Agency for Healthcare Research and Quality • CEBM = National Health Service Centre for Evidence-Based Medicine • EBM = evidence-based medicine • EBP = evidence-based practice • EBR = EBP in radiology • GCP = graph of conditional probability
Authors stated no financial relationship to disclose.
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TOPABSTRACTINTRODUCTIONSTEP 5: EVALUATECAVEATS AND COMMON QUESTIONSBOTTOM-UP EBP: EIGHT FREQUENTLY...References |
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This article has been cited by other articles:
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  L. S. Medina and C. C. Blackmore Evidence-based Radiology: Review and Dissemination Radiology, August 1, 2007; 244(2): 331 - 336. [Abstract] [Full Text] [PDF]
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W. Hollingworth and J. G. Jarvik Technology Assessment in Radiology: Putting the Evidence in Evidence-based Radiology Radiology, July 1, 2007; 244(1): 31 - 38. [Abstract] [Full Text] [PDF]
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E. J. R. van Beek and D. E. Malone Evidence-based Practice in Radiology Education: Why and How Should We Teach It? Radiology, June 1, 2007; 243(3): 633 - 640. [Abstract] [Full Text] [PDF]
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| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
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0.25—too high to dismiss. (b) Performance of CT, with summary statistics from four studies (level 4 evidence). Again, if the test is positive, appendicitis is ruled in. If the physician is operating at maximum clinical uncertainty, posttest probability of a negative test is <0.10, and if pretest probability is 0.75, posttest probability is <0.20. This is not perfect, but it is a better test performance than that with US. With very high pretest probability, further investigation may be indicated (eg, laparoscopy) even if the CT scan is negative. Images from both tests appear easier to interpret correctly when positive. Clinical information is needed for optimal interpretation of negative US and CT scans.
