Diagnosing acute myocardial infarction with troponins: how low can you go?. Issue 4 (12th April 2010)

• Record Type: Journal Article
• Authors: Body, Richard; McDowell, Garry; Carley, Simon; Ferguson, Jamie; Mackway-Jones, Kevin
• Is Part Of: Emergency medicine journal. Volume 27:Issue 4(2010)
• Page Start: 292
• Page End: 296
• Publication Date: 2010-04-12
• Subjects: Cardiac care -- cardiac care, diagnosis -- cardiac care, acute coronary syndrome; Emergency medicine -- Periodicals; 616.02505
• DOI: 10.1136/emj.2009.074948
• Languages: English
• ISSNs: 1472-0205

Abstract

Abstract : Background: Recent consensus guidelines state that acute myocardial infarction (AMI) may be diagnosed in the context of a troponin rise above the 99th percentile of the upper reference limit (URL) with the optimal imprecision of the assay (coefficient of variation, CV) being ≤10%. However, at the 99th percentile, modern assays do not have a CV ≤10%. Objective: The authors compared the prognostic implications of placing the diagnostic troponin cut-off at the 99th percentile and at the lowest concentration with a CV ≤10% (functional sensitivity). Methods: The authors prospectively recruited 804 patients presenting to the Emergency Department of a university-affiliated teaching hospital with suspected ACS. All patients underwent 12 h troponin T testing and were followed up by telephone and chart review. Outcomes: Death or AMI (excluding the index event) and the occurrence of major adverse cardiac events (MACEs) within 6 months. Results: Troponin T elevation below the functional sensitivity predicted the risk of death and AMI (adjusted OR 4.6, p=0.039) and MACE (adjusted OR 11.10, p<0.0001) independently of the Thrombolysis in Myocardial Infarction risk score and creatinine levels. Utilising the 99th percentile cut-off, an extra 17 MACEs could be predicted per 1000 patients treated at a cost of identifying 11 patients who would not have developed an event. Conclusions: The results suggest that adopting the lower troponin cut-off would reduce the proportion of 'false negatives' (patients with negative troponin who develop MACE) from 9.6% to 8.9%. Whether this reduction in 'false negatives' justifies the increase in 'false positives' warrants further investigation and discussion.