Diagnostic implications of an elevated troponin in the emergency department

To determine the proportion of initial troponin (cTn) elevations associated with Type I MI versus other cardiovascular and noncardiovascular diagnoses in an emergency department (ED) and whether or not a relationship exists between the cTn level and the likelihood of Type I MI.

In the ED, cTn is used as a screening test for myocardial injury. However, the differential diagnosis for an initial positive cTn result is not clear.

Hospital medical records were retrospectively reviewed for visits associated with an initial positive troponin I-ultra (cTnI), ≥0.05 μg/L. Elevated cTnI levels were stratified into low (0.05-0.09), medium (0.1-0.99), or high (≥1.0). Discharge diagnoses were classified into 3 diagnostic groups (Type I MI, other cardiovascular, or noncardiovascular).

Of 23,731 ED visits, 4,928 (21%) had cTnI testing. Of those tested, 16.3% had initial cTnI ≥0.05. Among those with elevated cTn, 11% were classified as Type I MI, 34% had other cardiovascular diagnoses, and 55% had a noncardiovascular diagnosis. Type I MI was more common with high cTnI levels (41% incidence) than among subjects with medium (9%) or low (6%).

A positive cTn is most likely a noncardiovascular diagnosis, but Type I MI is far more common with cTnI levels ≥1.0.