This highly sensitive blood test can save lives

A highly sensitive blood test is proving to be reliable in identifying patients with an increased risk of death in the month after surgery.

In a large study covering over 21,000 patients aged 45 and older from 23 hospitals in 13 countries, researchers measured blood levels of a protein called troponin in patients during the first six to 12 hours after surgery and over the next three days.

Surgery of any kind can be a major stress on the body’s organs and varying degrees of heart muscle injury after noncardiac surgery are often overlooked —over 90 per cent go undetected without troponin testing. Found in heart muscle, troponin is released into the bloodstream as a result of damage to the heart.

The study results showed that 1.4 per cent of patients died during the first 30 days post-surgery. After adjusting for variables commonly associated with 30-day mortality such as age, active cancer and history of chronic obstructive pulmonary disease, the researchers found that those patients who had higher levels of troponin (between 20 and 64 nanograms per litre) were at three times greater risk of death during the post-surgery 30-day period than those with lower levels (less than 5 ng/L). Patients with peak levels of troponin (above 1000 ng/L) were found to have a 29.6 per cent risk of 30-day mortality.

“This is the first large international study to establish thresholds of high-sensitivity troponin T that are independently associated with death within 30 days after non-cardiac surgery,” said P.J. Devereaux, director of cardiology at McMaster University in Hamilton, Ontario, and lead author of the study. “Our data show that unrecognized heart injuries may account for about one in four of the deaths that happen in the first 30 days after surgery.”

Earlier this year, the United States Food and Drug Administration approved a high-sensitivity troponin test for use in the US, a move which physicians had been waiting for, as the test had already been in use in other parts of the world to help diagnose myocardial infarction.

James Januzzi Jr., MD at Massachusetts General Hospital in Boston said the FDA approval is “of considerable importance.” “We test troponins in thousands of patients on a daily basis, and make significant treatment decisions on the basis of the results,” Januzzi said to TCTMD Online. “Chest discomfort is one of the most common diagnoses we see in the emergency department setting, and having a more sensitive test to identify or exclude acute myocardial infarction is a big step forward.”

Presenting the findings last month at a session of the American College of Cardiology in Washington, D.C., Devereaux agued that by quick and accurate testing of troponin levels, doctors will be able to intervene and provide treatment more effectively and more often. “At the moment I think there is very low-lying fruit that we’re ignoring that could actually help a lot of patients,” Devereaux said.

“Research supports that basic interventions like cholesterol drugs, like statins, Aspirin and ACE inhibitors have the potential to help these patients,” said Devereaux to Global News. “If we can identify early that a patient is having a heart injury we can step up that monitoring of those patients and then get them seen by a cardiologist or internist.”