Use of Cardiac Troponin Testing in the Outpatient Setting

Steven J. Ross, MD; Nikhil H. Shah, MD; Steve A. Noutong Njapo, MD; Daniel J. Cordiner, MD; David E. Winchester, MD, MS

Disclosures

South Med J. 2019;112(5):295-300. 

In This Article

Abstract and Introduction

Abstract

Objectives: 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.

Methods: 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.

Results: 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.

Conclusions: 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.

Introduction

Cardiac troponin (cTn) measurement is a useful tool for diagnosing myocardial infarction (MI). This process should be performed with serial cTn testing during the course of several hours in conjunction with close clinical observation and other recommended testing such as electrocardiograms (ECGs). Because of the potential for acute morbidity and mortality of MI, the majority of the evaluation should be performed in an emergency department (ED) or inpatient setting.[1] Chronic elevation of cTn is associated with many conditions other than MI, for example, renal insufficiency, heart failure, and cardiomyopathy.[1] The elevation of cTn also has been used as a marker for cardiac involvement of systemic diseases such as amyloidosis, myopathies, and systemic sclerosis-spectrum disorders.[2,3] With the development of newer high-sensitivity cTn assays (hs-cTn), some have suggested that cTn may be useful for monitoring and risk stratification in patients with coronary artery disease, heart failure, pulmonary hypertension, hypertrophic cardiomyopathy, and many other conditions.[4–9] Although outpatient cTn testing may be appropriate in some of the above circumstances, the outpatient utility of available standard-sensitivity cTn (ss-cTn) assays in the context of suspected MI is limited. In general, few studies have attempted to examine outpatient cTn ordering patterns, and little is known about how cTn is being used in the outpatient setting. We therefore conducted this investigation to assess the patterns of care for patients evaluated with ss-cTn in the outpatient context. We hypothesized that the majority of outpatient ss-cTn orders would be for the purpose of diagnosing possible MI. In addition, we evaluated the subsequent care provided to these patients to identify potential areas of improvement.

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