Positive predictive value of an elevated cardiac troponin for type I myocardial infarction in ED patients based on the chief complaint

Background: Cardiac troponin testing is used to aid the diagnosis of myocardial infarction (MI) in the emergency department (ED) for patients who present with a range of symptoms. From a clinical perspective, the distinction between MI due to acute coronary artery thrombosis (type I MI) and other forms of direct and secondary myocardial injury (type II MI) is very important. However, the positive predictive value (PPV) of an elevated troponin for diagnosing type I MI, based on clinical history, has not been described. The objective of this study was to determine the PPV of an elevated troponin for type I MI based on the ED chief complaint.

Methods: We retrospectively reviewed the medical records of 1772 consecutive patients who had a troponin ordered in the ED at a tertiary care center over the period of March 1, 2013, to April 30, 2013. The chief complaint was based on official ED coding. For patients with a positive troponin, 2 authors independently reviewed the electronic medical record pertaining to the index encounter and subsequent hospitalization to adjudicate the cause.

Results: There was a significant association between the PPV of an elevated troponin for type I MI and the chief complaint. Patients with a chief complaint of chest pain were significantly more likely to have a type I MI compared to those without (PPV 84% vs 20%; Adjusted Odds Ratio (AOR), 14.31; P < .0001). There was also a significant association between the rate of type I MI and the chief complaint in all patients who had a troponin drawn. Patients with a chief complaint of chest pain were significantly more likely to have a type I MI compared to those without (PPV 9.8% vs 1.3%; AOR, 7.34; P < .0001).

Conclusion: Applying information on the PPV of troponin for type I MI based on the clinical history could improve troponin utilization and clinical decision making.