In the cohort study conducted by a team from UC San Francisco and the University of Colorado School of Medicine, it was found that 23 percent of patients either received incorrect diagnoses or experienced delays in diagnosis. Of these cases, 17 percent resulted in temporary or permanent harm to the patient.

The study's results are published in the January edition of the Journal of the American Medical Association.

To determine diagnostic errors, the research team looked at 2,428 records of patients who had been admitted to 29 hospitals across the United States in 2019. A little over half of the patient records were male (54 percent), and the average age of the patient was 63.9 years old. Roughly two-thirds of the patients were white.

Patient cases were reviewed by two physicians trained in error adjudications. The physicians evaluated medical records for the presence or absence of diagnostic errors or underlying process issues or faults. Any records marked for fault were then reviewed more closely to determine what, if any, harm was caused as a result of the error.

The physicians had to agree on their assessment of the error and harm caused before finalizing their review; a third physician resolved any disagreements.

In total, 550 patients experienced a diagnostic error. Of these, 436 patients suffered temporary or permanent harm or death as a result of the error. Among the 1,863 patients who died, diagnostic errors were found to contribute to 121 of those deaths, accounting for nearly one in 10.

In 116 cases, diagnostic errors resulted in extended hospital stays. The most significant risks for diagnostic error were identified as issues in patient assessment and problems related to the ordering and interpretation of tests.