New Study in the Clinical Biochemistry Journal Identifies the Precise Magnitude of Change in Cardiac Troponin Required for Early Diagnosis of a Heart Attack

Beckman Coulter Diagnostics announces the publication of research results in the Clinical Biochemistry journal that identifies the precise magnitude of change in cardiac troponin required for early diagnosis of a heart attack (myocardial infarction, or MI), utilizing its Access AccuTnI+3 troponin I blood test. Beckman Coulter’s troponin-I assay has been clinically proven through a large, multi-center study and is the only troponin assay currently cleared by the U.S. Food and Drug Administration (FDA) that is directly aligned with the agency’s October 2010 guidance to manufacturers of troponin tests.

The Access AccuTnI+3 troponin I blood test is a paramagnetic particle, chemiluminescent immunoassay for the quantitative determination of cardiac troponin I (cTnI) levels in human serum and plasma using the Access 2 Immunoassay System or UniCel DxI Access Immunoassay System to aid in the diagnosis of myocardial infarction. The precise magnitude of change in the post-market cardiac troponin study data were not evaluated by FDA as part of the product’s 510(k) clearance.

Current clinical guidelines for MI diagnosis require demonstration of a rise and/or fall in troponin values (a protein released from damaged heart cells and detected in the blood) between samples collected in sequence following presentation to the Emergency Department. However, the guidelines do not quantify what a clinically significant rise and/or fall is—referred to as “delta” in literature. Without a defined delta, physicians do not have a consistent approach for diagnosing MI.

For the past several years, a majority of publications have suggested a percentage-change in troponin levels as the appropriate change criteria for determining if a patient has had a heart attack. However, this method has proven to not be fully reliable and more recent publications suggest that absolute values may perform better. The results of this new study recommend movement away from a percentage-change reading and rather to using an absolute difference by ng/mL change.

The study, which consisted of nearly 2,000 patients enrolled at 14 institutions, reports representative diagnostic performance that would be observed in clinical practice for early rule-in and rule-out of heart attacks, and demonstrated that absolute changes (0.01 or 0.02 ng/mL) performed significantly better than relative (percentage) changes at all time intervals after Emergency Department admission.

“Study results suggest that the majority of patients with myocardial infarction can be identified at earlier observation times, and support consensus recommendations for an optimal blood sampling protocol with troponin measurement on admission and three hours later,” said principal investigator and lead author Alan B. Storrow, MD, vice chairman for Research and Academic Affairs, Department of Emergency Medicine, Vanderbilt University. “Another key finding of the study is that rule-out (correct identification of patients without a heart attack) was nearly 100 percent when baseline troponin was less than the diagnostic threshold of 0.03 ng/mL and absolute delta troponin was less than 0.01 ng/mL.”

“As troponin values rose, the probability of myocardial infarction increased. Baseline troponin values greater than 0.20 ng/mL were associated with nearly 90 percent probability of myocardial infarction. Earlier rule-in and rule-out may potentially save patient lives,” said Paula Southwick, PhD, co-author and principal clinical research scientist at Beckman Coulter Diagnostics.

The results of this robust, clinical study were published as two companion articles in a special cardiac biomarkers issue of Clinical Biochemistry.