Are you interested in making your AMI diagnostic evaluation even less specific? Good! Because Brahms Thermo Fisher et al want to sell you a rapid copeptin assay to help with that.
Copeptin is a stable, terminal portion of the arginine vasopressin peptide. This peptide is released from the pituitary in response to cardiovascular hemodynamic stress and has a theoretical role in the diagnosis of acute myocardial infarction. The advantage copeptin may have over conventional troponin assays is detectable release in circulation preceding troponin.
In 1971 patients collected through their multi-center trial, 156 were diagnosed with AMI (7.9%). Upon presentation to the Emergency Department, 40 were STEMI. 281 patients had cTnI greater than 40ng/L, 97 of whom were subsequently diagnosed with nSTEMI. 1646 had cTnI less than 40ng/L, 19 of whom eventually were diagnosed with nSTEMI – a miss rate of 1.1%. Pretty good – but, obviously, we practice in a zero-miss world. Adding copeptin to this troponin-negative population with a cut-off of 14pmol/L decreased the miss rate to 0.5%. The specificity, of course, was useless – only 10 of 493 patients with positive initial copeptin and negative inital troponin went on to receive a diagnosis of nSTEMI.
So, the question is – would a negative copeptin change your practice? Is there a clinically important difference between a 1 in 100 miss rate vs. a 1 in 200 miss rate? These authors think adding copeptin to troponin will allow you to discharge a patient after the inital biomarker result – but I think this minimal incremental improvement in diagnostic performance doesn’t change whatever pathway the patient was already on, nor add much to a discussion of shared decision-making with the patient. They also don’t address a performance advantage compared to high-sensitivity troponin assays (which have, of course, their own issues).
These authors are pretty high on copeptin – but, then again, many of them are employed by or sponsored by the manufacturers of the copeptin assay.
“Copeptin Helps in the Early Detection Of Patients with Acute Myocardial Infarction: the primary results of the CHOPIN Trial”
http://www.ncbi.nlm.nih.gov/pubmed/23643595