Lab Tests: Get Everything You Need, But No More

Lab tests can diagnose many diseases, but too many can cause unnecessary problems.

What to test

Brian Smith, MD, chair of Yale Medicine's Department of Laboratory Medicine, says when it comes to lab tests, it is best not to go looking for trouble.

Credit: Robert A. Lisak

To test or not to test?
  • Patients may receive abnormal results from their lab tests, even when there’s nothing wrong with them.
  • Certain medications can alter lab test results.
  • Yale Medicine has systems in place to guard against unnecessary lab tests.
  • Yale faculty members have led a national charge to get healthcare providers to choose lab tests wisely.

Six thousand. That is how many different lab tests can be done for a patient, for anything from vitamin D levels to salmonella to Zika virus. But just because a test is available does not mean you should get it.

“A patient will visit their doctor and say, ‘Can you test me for Lyme disease?’ They don’t have any symptoms, they’d just like to know,” says Brian Richard Smith, MD, chair of Yale Medicine’s Department of Laboratory Medicine.

When it comes to lab tests, it is best not to go looking for trouble. Were a Lyme disease test to come back positive, it might mean that you’ve been exposed to the disease. Or it could be a “false positive,” which is common when there are no symptoms. The latter result could send doctor and patient down a path of unnecessary treatment, which can create its own unpleasant, or even harmful, effects.

“If you’re not having any problems from it, that’s OK,” Dr. Smith says. “We usually don’t need to worry about it.”

The problem with ‘normal’

Some patients will have abnormal results from their lab tests, even when there is nothing wrong with them. It is the mathematical outcome of how a test’s reference range is developed. The range is typically defined as the middle 95 percent of results from a healthy population. That means about 5 percent of healthy people will get a result that falls outside those values.

That’s because “our bodies are all unique,” Dr. Smith says. “We all look and act different. There’s a pretty wide range of what’s normal.”

Here is a little more math. Five percent of healthy people means 1 out of 20. If you get 20 or 30 tests—not a high number, given that a simple complete blood count alone looks at eight different values—chances are that one of your results will fall out of the reference range, even though you are healthy.

“In fact, those people are not abnormal,” Dr. Smith says. “They are perfectly normal, living a good life, not having any problems, but their lab tests will show up as being abnormal.”

Treatment uncertainties

Another reason to avoid unnecessary lab tests: They may deliver worrisome results that lead to further testing not needed for the patient’s overall condition.

Some test results can be helpful in guiding the treatment of a specific patient population but are meaningless for another group. One example is the test for the protein CA 125, which is often elevated in women with ovarian cancer. “As you treat these patients, you follow the values and see if they go down,” Dr. Smith says.

Checking up

A lab technician at Yale Medicine performs a test.

But if CA 125 happens to be elevated in a healthy woman, a physician may not know how to proceed. This becomes especially problematic if a person has ordered the lab test for herself, as some companies allow patients to do.
“About three years ago,” Dr. Smith says, “I got a call from a physician in the community, and he said, ‘Can you help me out? We have this lab test result problem.’” A young woman had ordered a bunch of lab tests (marketed as a “comprehensive wellness panel”) for herself; one was for CA 125. “Her test was outside the normal range—but not by a lot—and now nobody knew what to do with that result,” Dr. Smith says. The woman ended up getting transvaginal ultrasound examinations and additional blood tests. “Her doctors debated whether they’d actually have to do more than that, like take a surgical look,” Dr. Smith says.

As it turned out, the woman needed none of this. She was just one of those people whose lab test value for CA 125 fell slightly outside the normal range. “But it generated a lot of anxiety for her,” Dr. Smith says, adding that she faced additional costs and health risks from the tests. “If she had come in with a symptom that suggested ovarian cancer, it would have been a great idea to do this test,” Dr. Smith says. “But random screening? Not a great idea. That’s a general reason why we advise against doing a test without having a good reason.”

Tests have risks

Beyond confusing results, excessive testing can bring real harm, especially for people who are sick and in the hospital.

While it is not a problem for healthy people to lose a few tablespoons of blood for a lab test, those who are ill may not replace blood cells as quickly. Also, Dr. Smith says: “It’s very easy for the people taking care of the patient to say, ‘Let’s just check a whole bunch of lab tests every day, to make sure things are OK.’ So if you’re there for two weeks, you get your blood drawn every day. That adds up quickly.” The tests can be uncomfortable for the patient. They can stress and scar blood vessels and cause bruising. In rare cases, patients end up so depleted of blood that they become anemic—lacking in healthy red blood cells or hemoglobin—or even need a transfusion. “It usually doesn’t get that extreme, but we worry about that,” Dr. Smith says.

Yale Medicine has systems in place to guard against unnecessary lab tests. A priority is educating health care providers—physicians, advanced practice registered nurses, physician’s assistants and others—about when each test is appropriate. “We spend a lot of time on that,” Dr. Smith says.

Yale Medicine’s electronic test-ordering system is designed to ensure that patients get the right tests. The system offers information on each test’s most common uses and includes safeguards to help ensure that a provider does not order the wrong test.

The system also searches for details in the patient’s record, such as medications she is taking, that might affect results. If a patient is taking a drug that inhibits clotting, for example, a test of the blood’s clotting ability cannot be interpreted the same way as one for a person not taking those kinds of drugs. Certain drugs can also alter lab test results.

If a test is truly necessary, however, a health care provider can override the system. “You can always call and say: ‘No, I really need this,’ ‘The patient isn’t actually on that drug’ or whatever the reason,” Dr. Smith says.

‘Choosing wisely’

Protecting people from unnecessary lab tests is something Yale Medicine takes seriously, Dr. Smith says. Yale Medicine faculty members have helped to lead the charge on a national push to get health care providers—and their patients—to choose lab tests wisely.

“People should not have extra blood drawn, they should not have the extra expense and most importantly they should not get a confused picture of what’s going on with their health,” Dr. Smith says.

Ideally, patients should discuss their symptoms and concerns with their health care providers and come to an agreement about which tests to do and which to avoid. “It’s about partnering with your doctor to get the best care possible,” Dr. Smith says.