Why do clinicians continue to order ‘routine preoperative tests’ despite the evidence?

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Guidelines and practice advisories issued by several medical societies, including the American Society of Anesthesiologists,1 American Heart Association (AHA) and American College of Cardiology (ACC),2 and Society of General Internal Medicine,3 advise against routine preoperative testing for patients undergoing low-risk surgical procedures. Such testing often includes routine blood chemistry, complete blood cell counts, measures of the clotting system, and cardiac stress testing.

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In this issue of the Cleveland Clinic Journal of Medicine, Dr. Nathan Houchens reviews the evidence against these measures.4

Despite a substantial body of evidence going back more than 2 decades that includes prospective randomized controlled trials,5–10 physicians continue to order unnecessary, ineffective, and costly tests in the perioperative period.11 The process of abandoning current medical practice—a phenomenon known as medical reversal12—often takes years,13 because it is more difficult to convince physicians to discontinue a current behavior than to implement a new one.14 The study of what makes physicians accept new therapies and abandon old ones began more than half a century ago.15

More recently, Cabana et al16 created a framework to understand why physicians do not follow clinical practice guidelines. Among the reasons are lack of familiarity or agreement with the contents of the guideline, lack of outcome expectancy, inertia of previous practice, and external barriers to implementation.

It is harder to convince physicians to discontinue a current behavior than to implement a new one

The rapid proliferation of guidelines in the past 20 years has led to numerous conflicting recommendations, many of which are based primarily on expert opinion.17 Guidelines based solely on randomized trials have also come under fire.18,19

In the case of preoperative testing, the recommendations are generally evidence-based and consistent. Why then do physicians appear to disregard the evidence? We propose several reasons why they might do so.


The complexity of the evidence summarized in guidelines has increased exponentially in the last decade, but physician time to assess the evidence has not increased. For example, the number of references in the executive summary of the ACC/AHA perioperative guidelines increased from 96 in 2002 to 252 in 2014. Most of the recommendations are backed by substantial amounts of high-quality evidence. For example, there are 17 prospective and 13 retrospective studies demonstrating that routine testing with the prothrombin time and the partial thromboplastin time is not helpful in asymptomatic patients.20

Although compliance with medical evidence varies among specialties,21 most physicians do not have time to keep up with the ever-increasing amount of information. Specifically in the area of cardiac risk assessment, there has been a rapid proliferation of tests that can be used to assess cardiac risk.22–28 In a Harris Interactive survey from 2008, physicians reported not applying medical evidence routinely. One-third believed they would do it more if they had the time.29 Without information technology support to provide medical information at the point of care,30 especially in small practices, using evidence may not be practical. Simply making the information available online and not promoting it actively does not improve utilization.31

As a consequence, physicians continue to order unnecessary tests, even though they may not feel confident interpreting the results.32


A lack of transparency in evidence-based guidelines and, sometimes, a lack of flexibility and relevance to clinical practice are important barriers to physicians’ acceptance of and adherence to evidence-based clinical practice guidelines.30

Most physicians do not have time to keep up with the ever-increasing amount of information

Even experts who write guidelines may not be swayed by the evidence. For example, a randomized prospective trial of almost 6,000 patients reported that coronary artery revascularization before elective major vascular surgery does not affect long-term mortality rates.33 Based on this study, the 2014 ACC/AHA guidelines2 advised against revascularization before noncardiac surgery exclusively to reduce perioperative cardiac events. Yet the same guidelines do recommend assessing for myocardial ischemia in patients with elevated risk and poor or unknown functional capacity, using a pharmacologic stress test. Based on the extent of the stress test abnormalities, coronary angiography and revascularization are then suggested for patients willing to undergo coronary artery bypass grafting (CABG) or percutaneous coronary intervention.2

The 2014 European Society of Cardiology and European Society of Anaesthesiology guidelines directly recommend revascularization before high-risk surgery, depending on the extent of a stress-induced perfusion defect.34 This recommendation relies on data from the Coronary Artery Surgery Study registry, which included almost 25,000 patients who underwent coronary angiography from 1975 through 1979. At a mean follow-up of 4.1 years, 1,961 patients underwent high-risk surgery. In this observational cohort, patients who underwent CABG had a lower risk of death and myocardial infarction after surgery.35 The reliance of medical societies34 on data that are more than 30 years old—when operative mortality rates and the treatment of coronary artery disease have changed substantially in the interim and despite the fact that this study did not test whether preoperative revascularization can reduce postoperative mortality—reflects a certain resistance to accept the results of the more recent and relevant randomized trial.33

Other physicians may also prefer to rely on selective data or to simply defer to guidelines that support their beliefs. Some physicians find that evidence-based guidelines are impractical and rigid and reduce their autonomy.36 For many physicians, trials that use surrogate end points and short-term outcomes are not sufficiently compelling to make them abandon current practice.37 Finally, when members of the guideline committees have financial associations with the pharmaceutical industry, or when corporations interested in the outcomes provide financial support for a trial’s development, the likelihood of a recommendation being trusted and used by physicians is drastically reduced.38

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