• Cardiac troponin
• 99th percentile
• Myocardial Infarction

We have read with interest the paper by Collinson et al,1 and we are grateful for an opportunity to respond to their comments, especially those that relate to our recent BMJ paper describing the Is the current threshold for diagnosing raised highly sensitive troponin apparopriate for a hospital population? (CHARIOT) study.2

The use of more sensitive troponin assays in UK hospitals is now universal. The frontline clinical staff who request and then interpret the test belong to a wide range of clinical specialties. The concept for CHARIOT emerged out of our observations that there was an important mismatch in actual clinical practice between the extremely precise guidelines that lay out how these assays should be employed to rule out myocardial infarction (MI), or diagnose MI or myocardial injury, and their actual use. Specifically, there are important and widespread misconceptions about how troponin values should be or can be interpreted. First, that the manufacturer-provided 99th centile value for their assay represents a binary ‘upper limit of normal’ for a hospital population. Second, that a single troponin result above that 99th centile represents an ‘acute coronary syndrome’ diagnosis, regardless of whether there is an appropriate accompanying history. Third, that the general awareness that type 2 MI and myocardial injury are common, distinct clinical entities from type 1 MI, both pathophysiologically and in terms of appropriate management algorithms, …