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Laboratory testing is health care’s single highest volume activity, with more than 5 billion tests performed each year in the U.S.
A new study examining 15 years’ worth of published research reveals some surprising findings about blood tests.
Led by investigators at Harvard Medical School and Beth Israel Deaconess Medical Center and reported online in the journal PLOS ONE, the large-scale analysis of 1.6 million results from 46 of medicine’s 50 most commonly ordered lab tests found that, on average, 30 percent of all tests are probably unnecessary.
Even more surprising, the results suggest that equally as many necessary tests may be going unordered.
“Lab tests are used in all medical specialties, affecting virtually all patients,” said senior author Ramy Arnaout, HMS assistant professor of pathology and associate director of the clinical microbiology laboratories in the Department of Pathology at Beth Israel Deaconess.
“While working with my clinical colleagues around the hospital, I often found myself wondering about the appropriateness or inappropriateness of all of these tests. In developing this study, my coauthors and I wanted to learn more about overall lab test utilization so that we could better understand how and where errors were occurring in this extremely high-volume activity,” Arnaout said.
Their findings revealed a stark problem: Not only was there a 30 percent overall rate of test overuse, there was a similar rate of underuse.
While the authors found both overuse and underuse to be prevalent problems throughout laboratory testing, the overall findings point to a bigger issue, said Arnaout.
“It’s not ordering more tests or fewer tests that we should be aiming for, it’s ordering the right tests, however few or many that is,” he noted.
“Remember, lab tests are inexpensive. Ordering one more test or one less test isn’t going to ‘bend the curve,’ even if we do it across the board. It’s everything that happens next—the downstream visits, the surgeries, the hospital stays—that matters to patients and to the economy and should matter to us,” Arnaout said.
“This paper explores many of the nuances surrounding exactly how, when and why lab tests are ordered and misordered,” said Jeffrey Saffitz, HMS Mallinckrodt Professor of Pathology and chairman of pathology at Beth Israel Deaconess.
“Many times, the reasons for ordering tests seems to be based on dogma, the way it’s always been done. This comprehensive and meticulous analysis shows that there are patterns in laboratory test utilization that can reveal when we do a good job at ordering tests and where we need to do better,” Saffitz said.
To conduct the study, the authors undertook a thorough review of the medical literature. Going back to 1997—the year that the last previous review of lab tests had been conducted—Arnaout, together with first author Ming Zhi, an intern at Kaiser Permanente Santa Clara Medical Center, began by scouring a host of databases matching terms such as “laboratory,” “blood test,” “utilization,” “overuse,” and “underuse.” They came up with approximately 34,000 papers.
“We cast a wide net, then filtered things out and eventually got down to a couple of hundred papers on laboratory utilization,” said Arnaout.
Further refinement led to an examination of 42 papers covering 1.6 million orders of 46 of the 50 most commonly ordered lab tests. These ranged from common tests such as complete blood counts and basic metabolic panels to less common tests such as D-dimer (for pulmonary embolism) and HIV-1 tests.
From these measurements, they set about estimating the overall prevalence of inappropriate testing, including overuse (tests that are ordered but not indicated) and underuse (tests that are indicated but not ordered).
They also distinguished between inappropriate initial testing—during a clinician’s first evaluation of a patient or in response to new signs or symptoms—and inappropriate repeat testing, which occurs when the same tests are repeated—often multiple times—during a patient’s hospitalization.
“Most of the time when doctors talk about inappropriate lab testing, there’s a generally accepted notion that it’s too many ‘repeat’ tests being ordered,” said Arnaout.
“But, unexpectedly, on a per-test basis, we actually found that the main problem was tests being over-ordered during a patient’s initial examination, rather than during repeat tests. This indicates to us that ordering the right test during the initial evaluation may lead to fewer errors and better patient care,” he said.
The authors also established criteria that influence how doctors order lab tests and examined their final outcomes in the context of these criteria, for example, what they call restrictive vs. permissive criteria.
“In medicine, as a rule, we only do things if there is a reason,” said Arnaout. “You’d never have a situation where you drop a loved one off at the doctor and when you pick them up at the end of a day, they’re missing a foot because the doctor went down a checklist and couldn’t see any reason not to remove the foot. That doesn’t happen because medicine adheres to ‘restrictive’ policies. However, as our findings showed, laboratory medicine is the exception to this rule. In ordering blood tests, we too often tend to be permissive, asking ‘why not?’ instead of ‘why?’”
“These findings offer the field of pathology both an opportunity and challenge for the future,” added Saffitz.
“When it comes to appropriate lab testing, I think the pathologist has as much responsibility to get it right as the doctor who is ordering the test. This paper focuses attention on this important issue,” he said.
Adapted from a Beth Israel Deaconess news release.