It is no longer considered acceptable for medical practice to be based largely on clinical anecdotes, uncontrolled investigations and expert opinion. There are many flaws in this old paradigm. Reliance on expert opinion, so-called “eminence-based practice,” is based on that expert's biased individual experience: their practice mix, an overemphasis on recent events, small sample size, and lack of objectivity. Rather, medical decisions should be based on best available evidence. Evidence-based medicine (EBM) is recognized as a practice that should be learned and practiced by all radiologists, and indeed, by all physicians. When practiced effectively, EBM integrates clinical expertise, patients' values, and best evidence, and promotes optimal patient care.
The term EBM was officially coined in the early 1990s by clinicians and epidemiologists at McMaster University, Ontario. The definition of EBM is “the conscientious (meticulous and careful), explicit (clearly developed with nothing implied), and judicious (wise and sensible) use of current best evidence in making decisions about the care of the individual patient.”1 There are an increasing number of resources available to radiologists who want to learn how to apply the principles of EBM. These include a self-directed online EBM tutorial (Evidencebasedradiology.net), “how-to” articles in radiology journals,2 and webcasts and other continuing medical education offerings from radiology societies. The practice of EBM is enabled by the internet, development of systematic reviews, creation of evidence-based journals, and an emphasis on lifelong learning. Criticisms of EBM include its use as a political tool to curb costs, that it's time-consuming, it threatens autonomy in decision-making, there is insufficient information available, experts are frequently wrong, guidelines (recommendations) are often confused with standards (requirements) by lay people and lawyers, and individual needs are trumped by the greater good. Indeed, the success of EBM depends on having sufficient information at the right place, at the right time, and in the right format.
The original model of EBM consisted of a clinical question at the point of care, literature search, selection and evaluation of articles, and deciding what to do, all while the patient waited. In reality, this almost never happened. Today, EBM no longer means evaluating original research. It means finding good secondary sources that summarize the literature and provide a useful, actionable bottom line based on the evidence. Multiple sources are now available, including journals (one has only to search “EBM journals” online to find them), clinical guidelines (eg, the National Guideline Clearinghouse), and evidence summaries (eg, the Cochrane Database of Systematic Reviews and the “turning research into practice” or TRIP Database). The American College of Radiology Appropriateness Criteria® (http://www.acr.org) provides guidelines for imaging that are based on a review and group consensus of the best available evidence.3 Once this information is accessed, decisions should still take into account patient values (eg, cost, comfort, convenience, quality, accuracy, side effects, adverse reactions, reassurance, specific diagnosis, control, and autonomy). External evidence can inform but does not replace individual radiologic expertise.
EBM has been applied to cardiothoracic imaging through the development of numerous critically appraised topics, or CATs. These topics include screening and staging of lung cancer, coronary CTA, evaluation of aortic disease, use of CT pulmonary angiography, management of a solitary pulmonary nodule, and evaluation of patients with trauma to the chest. Summaries of evidence for questions related to each of these topics, along with suggested imaging protocols, are presented in one textbook, both in hard copy and electronic format.4
Evidence related to lung cancer screening supports CT and PET as the primary tools for staging non-small cell lung cancer and MRI for evaluating the brachial plexus. The utility of PET is to upstage or downstage. It detects unsuspected disease in the lung, mediastinum, or extrathoracic sites and avoids unnecessary thoracotomy in up to 20% of patients.5 Routine evaluation of bone metastases in patients with non-small cell lung cancer is not warranted in asymptomatic individuals. PET has similar sensitivity but much higher specificity and negative predictive value in evaluating for bone metastases compared with scintigraphy. Potentially operable tumors greater than 3 cm in size are most likely to benefit from routine screening for cerebral metastases and screening is not necessary for T1 tumors less than 3 cm in size. Contrast-enhanced head CT is as effective as contrast-enhanced MRI. PET has poor sensitivity and can't exclude cerebral metastases because the brain utilizes glucose at a high rate, obscuring metastatic uptake. In cases of small cell lung cancer, routine imaging of the central nervous system is warranted due to a high incidence of metastases, bone scintigraphy should be part of initial staging, and routine staging of the abdomen with CT or MRI is warranted (up to 60% of patients will have metastases in the abdomen at the time of diagnosis).
Evidence regarding the management of solitary pulmonary nodules supports no further evaluation if the nodule is stable for two or more years or is associated with a benign pattern of calcification (eg, central, “popcorn,” diffuse, or laminated) on chest radiography or CT.6 CT should be the initial test for most patients with indeterminate solitary pulmonary nodules as CT is relatively inexpensive, noninvasive, and highly specific for identifying some benign nodules. CT can exclude cancer when features of rounded atelectasis or a feeding artery and draining vein are demonstrated. Solid nodules 4-10 mm in size can be followed with CT at 6, 12, and 24 months. If greater than 10 mm, PET or biopsy is recommended. Part solid nodules should be considered separately from solid nodules and followed accordingly.
There are many more examples of how recommendations culled from a critical analysis of the literature can aid decision making in cardiothoracic imaging. EBM can be facilitated by the use of computerized physician order entry (CPOE) incorporating the ACR Appropriateness Criteria®. CPOE can track all imaging exams ordered and alert users when an exam is inappropriate or exceeds acceptable dose standards.
Learning how to apply EBM to one's practice can be the basis of a performance quality improvement project either independently or as part of the American Board of Radiology's maintenance of certification (MOC) program. Both EBM and MOC emphasize lifelong, self-directed learning.
1. Sackett DL, Rosenberg WMC, Gray JAM, et al. Evidence-based medicine—what it is and what it isn't BMJ.. 1996;312:71–72
2. The Evidence-Based Radiology Working Group. . Evidence-based radiology: a new approach to the practice of radiology Radiology.. 2001;220:566–575
4. Medina LS, Blackmore CC Evidence-Based Imaging: Optimizing Imaging in Patient Care. 2006 New York, NY Springer
5. Ravenel JG, Silvestri GAMedina LS, Blackmore CC. Imaging of lung cancer Evidence-Based Imaging: Optimizing Imaging in Patient Care. 2006 New York, NY Springer:57–78
6. Kumar A, Kazerooni EAMedina LS, Blackmore CC. Imaging of the solitary pulmonary nodule Evidence-Based Imaging: Optimizing Imaging in Patient Care. 2006 New York, NY Springer:417–440