The Effect of Hemolysis on Current Troponin Assays—A Confounding Preanalytical Variable?

The universal definition of myocardial infarction stipulates the detection of an increase and/or decrease in cardiac biomarkers [preferably troponin I (TnI)1 or T (TnT)], with at least 1 value >99th percentile of the upper reference limit, together with evidence of myocardial ischemia (1). With the emergence of more sensitive troponin assays, what constitutes a genuine increase and/or decrease becomes critically important(2). For analytical values to be considered different, it has been suggested that such values should vary by >3 SDs of the variance of the measurement method and that a 20% change for troponins is greater than what would be expected from analytical variation(1). At low troponin concentrations, either definition translates into small absolute changes. Good analytical precision is therefore critically important, as is careful consideration of preanalytical variables, such as sample type and particularly hemolysis. Hemolysis is known to be more prevalent in the emergency department environment, with rates of up to 20% of samples(3). Hemolysis is known to cause interference in both TnT and TnI assays(4), although such effects become even more important with the emergence of more sensitive troponin assays and the increased reliance on interpretation of small absolute changes. We therefore evaluated the degree of analytical interference from hemolysis with currently available troponin assays.