Background: The American Heart Association (AHA)
case definition for acute myocardial infarction (AMI)
requires an “adequate set” of biomarkers: 2 measurements
of the same marker at least 6 h apart. A sensitive
troponin assay might detect significant changes in concentration
earlier. We determined AMI prevalence, using
protocols with shorter intervals between measurements,
with and without incorporating the time from
onset of symptoms.
Methods: The AHA case definition was used to retrospectively
assign a diagnosis in 258 patients presenting
to the emergency department with symptoms of cardiac
ischemia. AMI was diagnosed if either specimen in an
adequate set had a cardiac troponin I (cTnI) above the
99th percentile (AccuTnI® >0.04 g/L; Beckman
Coulter) with a >20% change in concentration between
specimens. We assessed positivity for AMI after progressively
decreasing the time interval between specimens
in specimen sets. In addition, for each patient, 2
additional specimen pairs were selected: pairs collected