In the coming age of proteomics, biomarkers are going to aid tremendously — and in fact already have begun that process — in cardiac medicine, said Robert Christenson, PhD, professor of pathology and professor of medical and research technology at the University of Maryland School of Medicine (Baltimore).

He defined proteomics as "the study of the expression, function and interaction of proteins in health and disease," and said diagnostics is the "use of expression patterns as tools in the care of patients."

Cardiac troponin already is the primary biomarker used in the emergency department (ED) today, as are such tests as BNP (B-type natriuretic peptide) using natriuretic peptides, which are used for diagnosis of acute coronary syndrome.

The current use of several biomarkers has led to "new diagnostic strategies and approaches in hospital-based cardiac care," Christenson told listeners during an audioconference on cardiac biomarkers sponsored by the American Association for Clinical Chemistry (AACC; Washington) earlier this spring.

Frank Peacock, MD, emergency medicine vice chief of research and medical director, event medicine at the Cleveland Clinic, said ED physicians "look at things differently than they do in the cardiac world."

For example, if someone presents with chest pain in the ED, a physician's "miss rate {[in other words missing a person who is actually having or in danger of having a heart attack] must be less than 1%." If it is above that, he said, it becomes not only a matter for the hospital, but also for his career and then often spills over into the courtroom when families sue if a family member's death occurred that they believe could have been avoided.

And "speed is a must," he said, because ED physicians have to make rapid decisions as to whether to treat a cardiac event or diagnose some other cause of the problem.

As an example, Peacock said that there are about 100 million visits annually to EDs nationwide, of which 8 million involve possible cardiac-related problems. Of that 8 million, 2.5 million are dismissed as a non-cardiac issue. But it's critical to make the right decision, he said, because "a cardiac event at home is never a good outcome."

That's where cardiac panels come into play, because, as he said, "the cost of a test is less relevant [to the a hospital's costs] than an ED bed."

Troponin tests are the most commonly used biomarker tests in the ED today, and before a decision can be made whether to dismiss or admit a person, hospitals likely mandate that such a test have been conducted, Peacock said. Troponin is a protein released from dying heart muscle cells that are deprived of blood flow during a heart attack.

"That's very different than five years ago," he said, indicating the rapid rate of change since biomarker tests have become available.

The faster those decisions can be made using tests, the better not only for the patient, but also for physician administrators who are trying to save overall costs. Using a mathematical example, Peacock demonstrated that just by cutting an hour off a small percentage of admitted patient stays, it can save large sums of money for the hospital. But the decision needs to be the right one, he cautioned, noting at one point, "If I send them all home, it doesn't suit anyone well except my lawyer."

And whereas troponin levels do not seem to indicate a later increase in mortality, BNP tests do seem to be an indicator of patient mortality when looking at trends. BNP tests can be used for a variety of things, primarily for the diagnosis of acute coronary syndrome, but also for the prediction of survival in patients after myocardial infarction in conjunction with other risk factors, as well as assessment of heart failure severity in patients diagnosed with congestive heart failure.

What is expected to be in greater use in EDs in the future are panels involving several cardiac tests, rather than doing a few tests in serial order, because panels are "a much better strategy than any one test," Peacock told listeners.

And for anyone practicing medicine in the ED today, he cautioned, "If you're not using biomarkers right now, you're really putting yourself at risk."

Christenson told listeners from a laboratorian's point of view that more tests — meaning new tests — are not always better, although, for example, he said that the myoglobin test once commonly used has been "replaced in many places by troponin."

One of the most important issues to deal with in the laboratory as proteomics comes of age is not to "dumb down" the information that can be gleaned from tests for simplicity's sake, he said.

A third speaker, James de Lemos, MD, of University of Texas Southwestern Medical Center (Dallas), told listeners that the characteristics of an "ideal" cardiac biomarker include easy and reliable measurement, incremental diagnostic/prognostic value, guides clinical decision-making and is "cost-effective." Troponin, he said, is an example of just that.

However, all the speakers involved in the audioconference agreed that what will be needed in the near future are biomarker tests that can tell physicians if there is ischemia, for example, or other disease pathophysiology before the cardiac problem becomes an actual cardiac event.

Also, there is the question of how such tests will be reimbursed. Although he said he had few answers and welcomed suggestions from listeners, Christenson said no one wants them to break the bank.

"Altruism only goes so far," he said. "We really need a way to pay for this."