A person sits in a doctor's office wearing a hospital gown.

Having elective surgery? Your doctor may tell you that you need to get blood or urine tests, X-rays, or other medical tests ahead of time to detect any problems that could cause a complication during the procedure.

A blood test, for instance, could reveal—at least in theory—that your blood isn’t clotting properly, which may put you at risk for excessive bleeding.

For many people, however, these preoperative screenings don’t have much benefit in practice, according to experts. “For a healthy patient having a routine, low-risk procedure, preoperative testing is generally unnecessary,” says John Vassall, M.D., a member of the Choosing Wisely Task Force, a project of the Washington Health Alliance, the Washington State Medical Association, and the Washington State Hospital Association.

more on screening tests

A new study looks at the frequency of possible consequences of unnecessary testing before surgery. Researchers used the example of electrocardiograms (EKGs) before cataract surgery, a preoperative test deemed unnecessary for people who don’t already have heart disease by several professional societies and ample research. The study, published in JAMA Internal Medicine, found that about 16 percent of older adults who had an EKG before cataract surgery experienced one or more potential “cascade events,” such as follow-up tests, treatments, doctor’s visits, hospitalizations, or new diagnoses within 90 days.

When it comes to EKGs before cataract surgery, “knowing more is not always better and can lead to harm,” says the study's author, Ishani Ganguli, M.D., M.P.H., an assistant professor of medicine at Harvard Medical School and Brigham and Women’s Hospital. “Especially if you don’t know what you’re looking for.” And when it’s done without good reason, such testing can create extra costs and anxiety, and expose consumers unnecessarily to risks associated with additional tests and treatments.  

EKGs before cataract surgery are only one example of questionable preop tests. Here’s what else you need to know about tests before surgery and how to talk with your doctor about them.

The Problem With Preop Testing

In decades past, preop testing was considered essential to reveal undiagnosed conditions that might mean that a person couldn’t undergo surgery safely or might be unable to recover afterward. And some people should certainly have preop tests (see “Who Needs Preoperative Testing?” below). 

But today, “modern surgery is safer, and many surgeries are simpler, more routine, and less invasive,” Vassall says. Routine preoperative testing isn’t likely to uncover a condition that would keep someone from having elective surgery. (In emergency surgery, there’s often no time for preop testing.)

A great deal of research backs this up. A comprehensive analysis, updated in 2016 by the U.K.’s National Institute for Health and Care Excellence (PDF), evaluated 13 types of preoperative tests—including chest X-rays, lung function tests, complete blood counts, and urinalyses—and found that in most cases, they added no benefit.

And while many preoperative tests, such as blood and urine analyses, are relatively low-risk, there’s always the chance of a false positive, a result that indicates a potential problem where there actually isn’t one, says Matthew Rusk, M.D., a professor of clinical medicine at the University of Pennsylvania Perelman School of Medicine.

False positives can lead to additional testing, which can delay treatment and pose its own risks, or even lead to other treatments you don’t need, the cascade of care described in the new JAMA Internal Medicine study.

For instance, a routine preop chest X-ray might detect what looks like an abnormality in the lung, which may require follow-up testing to determine whether it’s lung cancer. And a lung cancer biopsy has the potential for serious risks, such as a collapsed lung.

With cataract surgery, evidence is clear that people who receive an EKG before have no lower risk of adverse events or complications, according to Ganguli. “It’s as arbitrary as doing an EKG before your morning coffee,” she says.

Who Needs Preoperative Testing?

In general, the healthier you are and the less risky the surgery, the less likely it is that you need to do more than provide a thorough medical history and have a physical exam before.

With cataract surgery, risks such as bleeding and heart problems are highly unlikely. That’s why the American Academy of Ophthalmology recommends against preoperative EKGs for this surgery and against all preop tests for cataract removal for otherwise healthy people.

What about blood and urine tests, which are commonly ordered before a variety of surgeries? According to the American Academy of Family Physicians (AAFP) and the American Society for Clinical Pathology, they should be done only in very specific instances.

For instance, the AAFP says a preop urine test is recommended only for people who are having an invasive urological surgery or are having a device, such as a heart valve, implanted.

If you have pre-existing medical conditions such as heart disease or diabetes, or you're older, you’re more likely to need some sort of preoperative testing before elective surgery. For example, the American College of Surgeons says that most people don’t need a chest X-ray before an ambulatory (or outpatient) surgery unless they have signs of an acute heart or lung problem, or they're 70 or older and have chronic heart or lung disease.

A complete blood count should be done only for people undergoing major surgery who are 65 or older or those who have (or are suspected of having) anemia, according to UpToDate, an online decision-making tool for healthcare professionals.

Talking to Your Doctor

Doctors may not always be up-to-date on preop testing recommendations, says John C. Matulis, D.O., M.P.H., an assistant professor of medicine in the division of community internal medicine at the Mayo Clinic. “As guidelines change, as current best practice changes, it’s hard for everyone to keep up,” he says.

You should always feel comfortable bringing up your concerns about tests and treatments, Vassall says. So if you’re having elective surgery and your doctor recommends one or more screening tests first, ask a few questions. Consider these five:

  • Does the test have any risks?
  • Is it recommended for me based on my health history?
  • What is the goal of the testing?
  • What can I expect from testing?
  • How might results change my surgery or treatment?