News: Probability of disease overestimated significantly by primary care providers

Primary care clinicians overestimate the probability of disease before and after diagnostic testing, which likely leads to overutilization of treatment that could harm patients, according to a study published in the Journal of the American Medical Association (JAMA) Internal Medicine and reported by HealthLeaders.

The research article is based on data collected from more than 550 primary care clinicians. Clinicians were asked to estimate the probability of the presence of disease in clinical scenarios before and after diagnostic tests for four conditions. The probability estimates were compared to the estimates of an expert panel that determined the probability of disease based on a literature review that included diagnosis textbooks.

The researchers found that the primary care clinicians overestimated the probability of disease for the following clinical scenarios before testing:

• For pneumonia, the median estimate of pretest probability of disease by the primary care clinicians was 80%, compared to a range from 25% to 42% for the expert panel
• For breast cancer, the estimate of pretest probability by the primary care clinicians was 5%, compared to a range from 0.2% to 0.3% for the expert panel
• For cardiac ischemia, the estimate of pretest probability by the primary care clinicians was 10%, compared to a range from 1.0% to 4.4% for the expert panel
• For urinary tract infection, the estimate of pretest probability by the primary care clinicians was 20%, compared to a range from 0% to 1% for the expert panel

The researchers found that the primary care clinicians also overestimated the probability of disease after positive test results as follows:

• For pneumonia, the estimated probability of the presence of disease by the primary care clinicians after positive radiology results was 95%, compared to a range from 46% to 65% for the expert panel
• For breast cancer, the estimated probability of the presence of disease by primary care clinicians after positive mammography results was 50%, compared to a range from 3% to 9% for the expert panel
• For cardiac ischemia, the estimated probability of the presence of disease by the primary care clinicians after positive stress test results was 70%, compared to a range from 2% to 11% for the expert panel
• For urinary tract infection, the estimated probability of the presence of disease by the primary care clinicians after positive urine culture results was 80%, compared to a range from 0% to 8.3% for the expert panel

Overestimation of the probability of disease can have negative consequences, the lead author of the research article told HealthLeaders.

"If doctors overestimate the chance of disease, they will often diagnose patients with diseases they do not have. There is no final test that is 100% accurate. Probability is central to making a diagnosis, and we need to consider probability both before and after testing…," said Daniel Morgan, MD, MS, professor of epidemiology, public health, and medicine at University of Maryland School of Medicine.

Editor’s note: This article was originally published by HealthLeaders. The JAMA internal Medicine published study can be found here.