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.