Understanding Where, Why, and How Diagnostic Errors Occur

“AHRQ has probably been the most important influence on my research career.
It has been central in generating new knowledge about the scope of errors and how to prevent them and make care safer.”

As an internist and an AHRQ-funded patient safety researcher, Eric J. Thomas, M.D., M.P.H., has long been intrigued by the topic of diagnostic errors.

His work as a practicing internist and professor of medicine at the University of Texas McGovern School of Medicine in Houston requires making multiple diagnoses each day, giving him a unique vantage point from which to investigate the problem. Dr. Thomas was one of the few researchers who identified the extent of patient harm caused by mistakes in diagnosis, and some of his early studies were cited in the Institute of Medicine’s 1999 landmark To Err is Human

report (PDF).

Supported by AHRQ, he has since delved into understanding where, why, and how often diagnostic errors occur—and how to reduce their frequency.

Using computerized triggers or algorithms to detect diagnostic errors in primary care settings, a 2007 AHRQ-funded study led by Dr. Thomas helped establish the magnitude of the problem. More than one-third of the nearly 200 cases he reviewed involved a missed diagnosis, most of them for common but potentially dangerous conditions such as pneumonia, heart and kidney failure, and cancer. These missed diagnoses, he determined, were largely due to process breakdowns in the patient-clinician encounter.

The role of process breakdowns in diagnostic errors wasn’t unexpected, but Dr. Thomas said he was “a little surprised at how frequently they were occurring.”

Determined to learn more, Dr. Thomas teamed up with fellow AHRQ grantee Hardeep Singh, M.D., M.P.H., to better quantify the frequency of diagnostic errors in outpatient settings. Drawing from three large studies, including Dr. Thomas’ earlier AHRQ study, the team established that diagnostic errors in primary care affect approximately 12 million U.S. adults each year, or 1 in 20 people. Their results were published in a 2014 study in BMJ Quality and Safety

Attaching a definitive number to diagnostic errors helped to clarify the scope of the problem, according to Dr. Thomas.

“It shows how important the problem is, so people are going to pay more attention to it,” he said. The study was cited in a 2015 report

(PDF) from the National Academy of Medicine (formerly the Institute of Medicine) that helped highlight the need for diagnostic safety research, which has since become a key Agency priority. AHRQ was a sponsor of the report.

In addition to his research in diagnostic errors, Dr. Thomas’ AHRQ-funded work has explored other major patient safety issues such as the impact of medical liability alternatives like non-disclosure agreements. One in three malpractice claims that result in death or disability stem from an inaccurate or delayed diagnosis, according to a 2019 study in Diagnosis.

His ongoing AHRQ-funded study aims to reduce preventable harms by half at the neonatal intensive care unit (NICU) at Memorial Hermann Hospital, which serves as the University of Texas teaching hospital. He is working with training and quality-improvement teams that include family members and caregivers.

“Many times, parents and family members are the only people who have the full story or complete view of what’s happening in the hospital,” he said. Parents have already provided input on a standardized NICU system at Memorial Hermann to prevent breathing tubes from being accidentally removed when infants are moved.

Dr. Thomas credits AHRQ with “being central in generating new knowledge about the scope of errors and how to prevent errors and make care safer. It’s hard to imagine we’d be able to make such progress without AHRQ.”

In addition to his academic appointments, Dr. Thomas is a member of the Society of General Internal Medicine and a fellow in the American College of Physicians. In 2007, he received the John M. Eisenberg Patient Safety and Quality Award from the National Quality Forum and The Joint Commission.

Principal Investigator: Eric J. Thomas, M.D., M.P.H
Institution: University of Texas Health Science Center, Houston
Grantee Since: 2001
Type of Grant: Various