Nav: Home

Blood test to diagnose heart attacks is flawed, warn researchers

March 13, 2019

The blood test used to diagnose a heart attack (acute myocardial infarction) in patients admitted to hospital can be misleading, warn researchers in a study published by The BMJ today.

Of 20,000 consecutive patients undergoing blood tests at University Hospital Southampton, one in 20 had levels of troponin (a protein released into the bloodstream during a heart attack) greater than the manufacturer's recommended upper limit. But in most of these patients were being seen for other conditions and so there were no clinical signs or symptoms of a heart attack.

Troponin levels also differed according to several factors such as age, sex and whether inpatient or outpatient.

The researchers, led by cardiologist Professor Nick Curzen, say these results highlight the need for medical staff to interpret troponin levels carefully in order to avoid misdiagnosis of a heart attack and inappropriate treatment.

Current guidelines recommend troponin tests to help exclude or diagnose a heart attack. Manufacturers of troponin tests provide a recommended level (known as the 99th centile) based on values from a few hundred healthy individuals.

This recommended level is used as the upper limit of normal (ULN). In other words, if the value of troponin is above the 99th percentile, that is considered to be abnormal, and would indicate a heart attack in appropriate clinical circumstances.

But little is known about the true distribution of the troponin level across a whole hospital population that includes inpatients, outpatients, patients undergoing surgery, in intensive care etc.

So researchers measured levels of high sensitivity cardiac troponin I (hs-cTnI) in 20,000 inpatients and outpatients undergoing blood tests for any reason at University Hospital Southampton between 29 June and 24 August 2017.

The average age of participants was 61 and 53% (10,580) were women.

The researchers found that the 99th centile of troponin for the whole study population was 296 ng/L compared with the manufacturer's recommended level of 40 ng/L.

One in 20 (1,080; 5.4%) of all 20,000 patients had a troponin level greater than 40 ng/L, but in most of these patients there was no clinical suspicion of a heart attack.

Overall, 39% of all patients from the critical care units, 14% of all medical inpatients, and 6% of all patients from the emergency department had a troponin concentration greater than the recommended ULN.

This is an observational study, and as such, can't establish cause, and the researchers point to some limitations, such as relying on patient records for details about management and diagnoses, and being unable to examine clinical outcomes.

Nevertheless, they say this study shows that "the 99th centile of high sensitivity troponin I concentration of the population in our hospital was substantially higher than the manufacturer's recommended ULN used in clinical practice based on the 99th centile for a healthy population."

These data "highlight the need for clinical staff to interpret hs-cTnI concentrations carefully, particularly when applying the recommended ULN to diagnose acute myocardial infarction, in order to avoid misdiagnosis in the absence of an appropriate clinical presentation," they conclude.
-end-
Externally peer-reviewed? Yes
Type of evidence: Observational
Subjects: People

BMJ

Related Heart Attack Articles:

Muscle protein abundant in the heart plays key role in blood clotting during heart attack
A prevalent heart protein known as cardiac myosin, which is released into the body when a person suffers a heart attack, can cause blood to thicken or clot--worsening damage to heart tissue, a new study shows.
New target identified for repairing the heart after heart attack
An immune cell is shown for the first time to be involved in creating the scar that repairs the heart after damage.
Heart cells respond to heart attack and increase the chance of survival
The heart of humans and mice does not completely recover after a heart attack.
A simple method to improve heart-attack repair using stem cell-derived heart muscle cells
The heart cannot regenerate muscle after a heart attack, and this can lead to lethal heart failure.
Mount Sinai discovers placental stem cells that can regenerate heart after heart attack
Study identifies new stem cell type that can significantly improve cardiac function.
Fixing a broken heart: Exploring new ways to heal damage after a heart attack
The days immediately following a heart attack are critical for survivors' longevity and long-term healing of tissue.
Heart patch could limit muscle damage in heart attack aftermath
Guided by computer simulations, an international team of researchers has developed an adhesive patch that can provide support for damaged heart tissue, potentially reducing the stretching of heart muscle that's common after a heart attack.
How the heart sends an SOS signal to bone marrow cells after a heart attack
Exosomes are key to the SOS signal that the heart muscle sends out after a heart attack.
Heart attack patients taken directly to heart centers have better long-term survival
Heart attack patients taken directly to heart centers for lifesaving treatment have better long-term survival than those transferred from another hospital, reports a large observational study presented today at Acute Cardiovascular Care 2019, a European Society of Cardiology congress.
Among heart attack survivors, drug reduces chances of second heart attack or stroke
In a clinical trial involving 18,924 patients from 57 countries who had suffered a recent heart attack or threatened heart attack, researchers at the University of Colorado Anschutz Medical Campus and fellow scientists around the world have found that the cholesterol-lowering drug alirocumab reduced the chance of having additional heart problems or stroke.
More Heart Attack News and Heart Attack Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.