Use of Cardiac Troponin Testing in the Outpatient Setting

Cardiac troponin (cTn) measurement is useful for diagnosing myocardial infarction (MI), particularly in the inpatient setting. A growing body of literature suggests that cTn may be useful for evaluating chronic conditions in the outpatient environment; however, little is known regarding cTn ordering patterns in this setting. We sought to investigate patterns of care and outcomes for patients evaluated with cTn in the outpatient setting. We hypothesized that a majority of outpatient cTn orders would be for the purpose of diagnosing possible MI.

We analyzed 228 patients who had outpatient orders for standard-sensitivity troponin T assays placed at our institution between January 1, 2013 and December 18, 2015. Data were divided into two cohorts based on the intended utility of cTn measurement: orders placed to evaluate for possible MI versus orders placed for some other purpose.

Of the 228 patients, 161 were evaluated for possible MI and 67 for other reasons. Risk factors (hypertension P = 0.32, diabetes mellitus P = 0.41, coronary disease P = 0.38, heart failure P = 0.098, and chronic kidney disease P = 0.70) were similar between the cohorts. In the suspected MI cohort, an electrocardiogram was obtained in only 77% of patients, and only 13.1% were sent to the emergency department (ED) for further evaluation. Within the suspected MI cohort, 10.5% (n = 17) had elevated cTn and the majority of these patients (n = 10) were not sent to the ED.

The majority of outpatient cTn orders were intended to evaluate for MI, although electrocardiograms were frequently not ordered and few patients were sent for further ED evaluation. Providers should be encouraged to use cTn testing in a manner that minimizes the potential risk to patients with possible MI.