Newswise — Primary care practitioners often over-estimate the likelihood of a patient having a medical condition based on reported symptoms and laboratory test results. Such overestimations can lead to overdiagnosis and overtreatment, according to a recent study conducted by researchers at the University of Maryland School of Medicine (UMSOM) published in JAMA Internal Medicine.

“A large gap exists between practitioner estimates and scientific estimates of the probability of disease,” said study leader Daniel Morgan, MD, a Professor of Epidemiology & Public Health at UMSOM. “Practitioners who overestimate the probability of disease might use that overestimation when deciding whether to initiate therapy, which could lead to the overuse of risky medications and procedures.”

To conduct the study, Dr. Morgan and his colleagues surveyed 553 primary health practitioners, including residents, attending physicians, nurse practitioners and physician assistants, in Maryland and seven other states. Survey respondents were asked to determine how well they could estimate the risk of four well-known health conditions based on hypothetical diagnostic scenarios. The researchers found, based on symptoms and test results, that health care providers significantly overestimated the likelihood of conditions. For example, health care providers, on average, estimated a 70 percent likelihood of cardiac ischemia in patients who had a positive finding on a stress test. In reality, based on evidence from medical studies, the real likelihood of  cardiac ischemia  is 2 to 11 percent.

The study also found that survey respondents estimated a 50 percent risk of breast cancer after a positive finding on a mammogram when evidence suggests 3 to 9 percent chance of breast cancer. They estimated an 80 percent likelihood of a urinary tract infection from a positive urine culture, and the vast majority of survey respondents said they would treat with antibiotics in these cases. The real risk of a UTI with a positive urine culture, however, is at most 8 percent.

“Solving this problem is not about asking health care providers to memorize numbers or practice math in order to improve their understanding of risks,” Dr. Morgan said. “We should, however, use probability and better utilization of decision-making tools to help them make better estimates.”

He developed a free tool called Testing Wisely, funded by the National Institutes of Health, that is designed to improve clinician understanding and ordering of diagnostic tests to make patient care safer. The site also includes a risk calculator to assess patients’ symptoms, exposure, and local positivity rates where they live to calculate their individual risk of having COVID-19.  

“Informed medical decision-making is incredibly important, and physicians should have access to tools that make their job easier and improve patient safety,” said E. Albert Reece, MD, PhD, MBA, Executive Vice President for Medical Affairs, UM Baltimore, and the John Z. and Akiko K. Bowers Distinguished Professor and Dean, University of Maryland School of Medicine. "This study demonstrates the need for better decision-making tools to help healthcare providers provide the best possible care to their patients.”

About the University of Maryland School of Medicine

Now in its third century, the University of Maryland School of Medicine was chartered in 1807 as the first public medical school in the United States. It continues today as one of the fastest growing, top-tier biomedical research enterprises in the world -- with 45 academic departments, centers, institutes, and programs; and a faculty of more than 3,000 physicians, scientists, and allied health professionals, including members of the National Academy of Medicine and the National Academy of Sciences, and a distinguished two-time winner of the Albert E. Lasker Award in Medical Research.  With an operating budget of more than $1.2 billion, the School of Medicine works closely in partnership with the University of Maryland Medical Center and Medical System to provide research-intensive, academic and clinically based care for nearly 2 million patients each year. The School of Medicine has more than $563 million in extramural funding, with most of its academic departments highly ranked among all medical schools in the nation in research funding. As one of the seven professional schools that make up the University of Maryland, Baltimore campus, the School of Medicine has a total population of nearly 9,000 faculty and staff, including 2,500 student trainees, residents, and fellows. The combined School of Medicine and Medical System (“University of Maryland Medicine”) has an annual budget of nearly $6 billion and an economic impact more than $15 billion on the state and local community. The School of Medicine, which ranks as the 8th highest among public medical schools in research productivity, is an innovator in translational medicine, with 600 active patents and 24 start-up companies. The School of Medicine works locally, nationally, and globally, with research and treatment facilities in 36 countries around the world. Visit



Journal Link: JAMA Internal Medicine