Technologies to measure cardiac troponin (cTn) and assess heart attack risk are developing rapidly and gaining influence in the United States. On August 1, leading researchers and educators will discuss in-depth the use and interpretation of high-sensitivity (hs) assays at the 70th AACC Annual Scientific Meeting & Clinical Lab Expo.
Real Global News: It’s Time to Embrace High Sensitivity Cardiac Troponin Assays With Cost Benefit Strategies For Early Rule-Out and Rule-In of Myocardial Infarction (34218), will take place from 2:30 p.m. to 5 p.m. and is worth 2.5 CE hours.
Proper implementation of hs-cTn assays calls for all stakeholders—labs, emergency, and cardiology providers—to assemble in the same room and discuss these issues. “Cardiologists look to each other for support and emergency physicians look to their colleagues as well,” session co-presenter Allan Jaffe, MD, chair of the division of clinical core laboratory services at Mayo Clinic in Rochester, Minnesota, told CLN Stat. The problem is different sectors emphasize different things. Emergency physicians are mostly concerned about sensitivity; cardiologists are much more interested in specificity. “We need some education around this. It’s terribly important that all of the groups get together” and find a consensus on hs-cTn testing, Jaffe suggested.
Jaffe, a leading researcher and educator involving the use and interpretation of cTn assays will be joined by two other globally recognized cTn testing experts. The session moderator will be Fred Apple, PhD, medical director of clinical laboratories, clinical chemistry, clinical and forensic toxicology, and point-of-care testing at Hennepin County Medical Center and professor of laboratory medicine and pathology at the University of Minnesota in Minneapolis. Rounding out this trio of highly regarded cTn authorities will be Richard Body, MB ChB, MRCSEd(A&E), FCEM, PhD, of Manchester Royal Infirmary in England, who will offer the European perspective on hs-cTn assays.
Apple plans to discuss how cTn fits into clinical lab practice, focusing on practice recommendations the AACC Academy and IFCC Task Force on Clinical Applications of Cardiac Bio-Markers published in Clinical Chemistry. He’ll address the role of detecting cTn with hs assays in early rule-out of myocardial infarction (MI), how clinicians should define the 99th percentile to guide decisions on ruling in MI, and when blood should be drawn to optimize diagnostics.
The aim is to educate emergency physicians, cardiologists, and hospitalists on the use of hs-cTn assays and why these tests are so effective for determining early rule in and rule-out of MI, Apple said. This session also will help clinical laboratory professionals understand the importance of assay analytics to move from contemporary assays currently in use to hs tests, Apple said.
The clinical applications of Roche Diagnostics’ Elecsys Troponin T (TnT) Gen 5 Stat, which in 2017 received U.S. Food and Drug Administration (FDA) clearance as an aid in diagnosing acute MI will be a key topic. “The question is, how do you use that testing?” Jaffe said.
Criteria issued by international experts specify that hs-cTn assays: should be able to meet the cutoff value of the 99th percentile at high rates of precision and at the very least, detect values of 50% of normal individuals. The reality is not all studies with cTnT have met that metric, Jaffe said.
The Elecsys Troponin T (TnT) Gen 5 Stat takes less than 10 minutes to diagnose acute MI. However, its 99th-percentile upper-reference limit values for acute MI suggested for use in the U.S. don’t match up to hs-cTn assays used in Europe, creating additional complications for its use by U.S. clinical labs. Jaffe endorses the European cutoff values based on his own studies.
“Europeans have a very different way of looking at some of these things. So the question is, what can the United States learn from our European colleagues who have been using this technology for at least eight years?” Jaffe said. “The nice thing about having Richard [Body] join us is being from the United Kingdom, he has the experience of dealing with some of the issues that have concerned clinicians and that our clients are going to concerned about.” Body will present on early, rapid rule-out strategies and safety performance at 30 days.
The concept of using hs assays to do a single sample rule-out has had good reproducibility in Europe. In this strategy, clinicians test the first blood sample of a patient who presents to the emergency department with chest discomfort. The patient can be ruled out of having acute MI if the cTn value is very low. “But there are some caveats to this,” Jaffe cautioned. It’s true that comorbidities leading to MI and disease often cause modest cTn elevations. However, this formula may not be applicable to all patients. Jaffe also questions whether hs-cTn assays are capable of ruling out acute MI in patients who present very early after the onset of symptoms because that is the group that more likely could be missed, and it is a markedly understudied group in most published reports.
Some data suggest that this strategy works optimally with low-risk patients. However, FDA is not allowing clinicians to report down to the really low values that are used in Europe. Jaffe believes that a single sample rule-out may be plausible someday as assays improve in their precision. Personally, he’s not in favor of a 1-hour rule-out because the imprecision of the hs-cTnT assay is not adequate in his opinion to make the distinction between a value of 3 and 5, which is what is required. “We at Mayo use the 2-hour rule-out instead,” which is still substantially less than previously used 4- and 6-hour rule out, he said.
On the rule-in side of MI, European studies have validated short interval protocols in a selected group of patients. “The problem is, there’s a whole other group of patients where this approach doesn’t work well,” Jaffe said. The European research left out many important subsets of patients, including the critically ill patients or those with renal failure, for example. Elderly patients were also underrepresented. The way the European protocol is currently set up, the likelihood for heart attack is very high for the subset of patients for whom clinicians primarily concerned about ruling out MI. But if you included these other subgroups, the specificity would go way down, Jaffe said.
If you don’t do that you have to establish different rule-in approaches for these other groups. By establishing different rule-in approaches for different people, “there’s going to be a lot of confusion,” he said.
The bottom line is the United States has to develop its own strategy for the use of hs-cTn assays. “We have to take into account all of the comorbidities and mechanisms of injury that clinicians measure cardiac troponin for in the United States that aren’t always measured for in Europe,” Apple said.
Register today to participate in this detailed scientific session at the 70th AACC Annual Scientific Meeting & Clinical Lab Expo July 29–August 2 in Chicago.