An estimated 8.5 million patients may have been tested for cardiac biomarkers despite the absence of acute coronary syndrome (ACS) symptoms, according to a study published in the January issue of JAMA: Internal Medicine.

Researchers from the University of Texas Southwestern Medical Center in Dallas found that of approximately 28.6 million visits, 30 percent were potentially inappropriate. Approximately 25 percent of patients tested for cardiac biomarkers had chest pain.

The estimates came from reports submitted to the National Hospital Ambulatory Medical Care Survey (NHAMCS) for 2009 and 2010. The survey provides a representative sample of patients presenting to U.S. emergency rooms that ultimately correlates to broader nationwide statistics.

Anil N. Makam, MD, MAS, and Oanh K. Nguyen, MD, MAS, organized visits into groups that included patients who did not have symptoms of ACS, those who had atypical symptoms and those who had clear symptoms of ACS. They found that patients who were admitted to the emergency department were more likely to be tested for cardiac biomarkers if they were undergoing more tests or services, particularly in the absence of ACS-related symptoms.

Among all patients, there was a 6.3 percent chance of being tested for cardiac biomarkers if they underwent zero to five tests, 34.2 percent for six to 10 tests, and for more than 10 tests, the likelihood of cardiac biomarker testing was 62.3 percent. They wrote that their findings suggested “cardiac biomarker testing may be a consequence of overall high-volume testing behavior.”

Subsequent hospitalizations with biomarker testing occurred in 38.2 percent of visits by individuals without ACS symptoms and 41.6 percent of patients who arrived at the emergency room based on poisoning or injury.

“The high rate of testing among individuals with low suspicion of ACS is concerning because of the potential increase in health care costs and downstream harms owing to false-positive results,” Makam and Nguyen wrote. Their concerns for consequences of unnecessary cardiac biomarker testing included further inappropriate testing and treatment, unnecessary cardiology consultations and hospitalizations and other unnecessary costs, services or patient stress.

They cautioned that the association between cardiac biomarker and high-volume testing may be related to other factors, including biobehavioral, comorbid or other clinical findings not included in the NHAMCS data. Still, they noted that further attention was needed to better understand the risks and strategies surrounding appropriate cardiac biomarker testing use and that guidelines should be developed to avoid misuse and long-term harms.