Blood test may help ID more at-risk patients

Quandary: Short of breath, but absent heart failure

According to a new study in the Archives of Internal Medicine,1 ED managers may be able to predict with greater accuracy than ever before the risk of post-discharge mortality in patients presenting with shortness of breath — whether they are diagnosed with heart failure.

Researchers from Massachusetts General Hospital in Boston have shown that the blood test measuring levels of the protein N-terminal prohormone brain natriuretic peptide (NT-proBNP), previously found useful for diagnosing heart failure and determining prognosis in several cardiovascular conditions, also can predict the risk of death among patients coming to hospital EDs with shortness of breath.

"There had really been no reliable single estimate that could be reproduced on a large scale for predicting such risk," notes James Januzzi Jr., MD, associate director of the coronary care unit, and the paper’s lead author. "For patients rolling into the ED with shortness of breath, there are so many diagnoses you need to consider, and not until now have we had a single, objective, rapid way of assessing a breathless patient’s risk for mortality."

Specifically, the study showed that an elevated value of more than 1,000 identified a patient with a threefold increase of risk for death in one year. "If you look at the converse, if you were below the cut point, the risk for mortality was so much lower it was dramatic," adds Januzzi. In the patients with heart failure who had a reading of less than 1,000, not a single one was dead one year after discharge, he observes. "In those patients without heart failure, mortality was well below 5% if they were below the cut point."

Perhaps the most important take-home message for ED managers is that the value and potential applications of this blood test have clearly expanded, says Januzzi.

"Initially, it was used to help identify and exclude heart failure, and that’s correct," he says. "Now, it’s shown value even for those patients who do not have heart failure — those with acute coronary syndrome, pulmonary embolism, and those who are just dyspneic [unable to breathe]."

The bottom line, he says, is that "rather than holding [this test] in your back pocket for patients for whom you are not sure what the diagnosis is, we are arguing that more widespread testing would be indicated, given its value for prognosis," he says. "In other words, we probably should be testing more patients."

Andrew Nugent, MD, vice chair of emergency medicine at the University of Iowa Healthcare in Iowa City, says he could go along with that statement, but it’s difficult for him to recommend the blood test for all patients. "It’s an awfully expensive thing to do, and I’m not sure how many people die within a year is that applicable to emergency medicine," Nugent says. "Frankly, I’d like to know the ones who are going to die today."

Nugent says he would like to see more information before recommending widespread use of the test. "I’d like to see the study taken further, perhaps to several hundred patients, and the types of patients [who would benefit most] narrowed down further," he says.

At present, Nugent reserves the tests for cases where he has a high degree of suspicion of congestive heart failure. "They say it’s applicable to others, but I’d have to find that group of patients and their complaints," he explains.

Potential liability implications

The study’s findings may have some liability implications, Januzzi says.

"There is a potential liability to missing heart failure, so with such high sensitivity, we can minimize this," he says. "Furthermore, recognizing that patients below a certain cut point have very low risk for mortality will lend further reassurance of a confident discharge."

More widespread testing will be more useful in picking up those patients with missed heart failure and inappropriate discharge, he says, "but it’s very hard to discharge someone with shortness of breath."

Of course, as many ED managers know all too well, patients’ families often will sue in the wake of a bad outcome — despite the fact that the patient may have received appropriate care. Might the use of this test mitigate liability for discharged patients who subsequently die several months later? It might, Nugent concedes. "It really depends on the patient," he says. "But when we send a patient out, we usually send them to someone who will hopefully do the right thing."

Even Januzzi has at least one very important unanswered question. "If the patient’s NT-proBNP comes back elevated, and they are without heart failure, we don’t yet know if directed treatment will be associated with better outcomes," he says.

Reference

  1. Januzzi JL, Sakhuja R, O’Donoghue M, et al. Utility of amino-terminal pro-Brain Natriuretic Peptide testing for prediction of 1-year mortality in patients with dyspnea treated in the emergency department. Arch Intern Med 2006; 166:315-320.