Despite an increasing emphasis on evidence-based practice, a new study in NEJM finds that many physicians still do not follow best practice guidelines for certain procedures, Anders Kelto writes for NPR's "Shots."

For the study, Catherine Chen, an anesthesiologist at the University of California-San Francisco, collected data on the number of doctors who follow clinical guidelines when performing cataract surgery. Cataract surgery, which Chen describes as a "prototypical low-risk surgery" that is "relatively painless and quick," involves replacing an eye's cloudy lens with a clear, prosthetic one.

According to clinical guidelines enacted in 2002, no preoperative testing—like X-rays, EKGs, or blood tests—is needed before preforming the operation, as such testing does not benefit individuals who are having a cataract removed .

But despite the guidelines, Chen found that 50% of ophthalmologists who performed cataract surgery on Medicare beneficiaries in 2011 ordered preoperative tests before surgery—the same percentage as in 1995, seven years before the guidelines were developed.  "In about 20 years, nothing has really changed in terms of physician performance," Chen concluded.

Residents follow doctors' orders—even when they're wrong

Steven Brown, a professor of family medicine at the University of Arizona, says there are several reasons doctors are reluctant to follow clinical guidelines, including:

• Belief that the patient is more likely to have a positive surgical outcome  if they undergo testing before;
• Lack of knowledge about the most recent guidelines; or
• The misguided idea that a clinician down the line will require the test anyway.

"[It becomes] this game of tag, where you're doing something because somebody else wants it, even if you don't really want it," says Brown.

Medscape: What's the difference between 'defensive' and 'careful' medicine?

While guidelines for some procedures are straightforward, recommendations for others can sometimes be conflicting when different interest groups present competing messages. 

For instance, draft recommendations released Monday by the U.S. Preventive Services Task Force (USPSTF) say mammograms for women in their 40s should be based on "informed, individualized decision making," as the procedure has the capacity to do more harm than good for those individuals.

The task force said that "most will not" benefit from mammograms "while others will be harmed," with such harms including women undergoing chemotherapy, radiation, or surgery for cancers that do not threaten their health. USPSTF also cited the risk of over-diagnosis.

However, both the American Cancer Society and the American College of Radiology recommend annual mammograms for women beginning at age 40.

Malpractice suits have changed standards of care, JAMA study finds

Albert Wu, an internist and professor at the Johns Hopkins Bloomberg School of Public Health, says, "There's really a lot more ambiguity about what is the right thing—what's appropriate [and] what's not appropriate." As a result, says Wu, physicians often rely on their guts, which can drive them to fear-based decision- making.

He notes that a doctor would likely oblige a 40-year-old woman if she were to request a mammogram, despite the USPSTF recommendations. He says, "If that woman were to develop breast cancer or to have breast cancer, you can imagine what might happen to you if you didn't order the test. Maybe you'd get sued." So, he says, "Emotion and recent events do influence our decision-making. We are not absolutely rational, decision-making machines" (Kelto, "Shots," NPR, 4/22).

According to the U.S. Congress of Technology Assessment, "defensive medicine" is defined as physicians ordering tests, procedures, or visits, or avoiding high-risk patients or procedures "primarily (but not necessarily solely) to reduce their exposure to malpractice liability."

Unsurprisingly, defensive medicine is expensive and has contributed significantly to the rise in health care spending—but experts say it's hard to draw a line between being appropriately cautious and overly aggressive.

Clinical decision support (CDS) is an effective way to support physician decision-making with evidence-based guidelines. When executed properly, CDS can ensure appropriate use of imaging by reducing utilization in the ED and the inpatient and outpatient settings.

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