Abstract 15339: Implications of Lowering the Threshold of Plasma Troponin in the Diagnosis of Myocardial Infarction
Background: The universal definition recommends the 99th percentile of plasma troponin as the diagnostic threshold for myocardial infarction (MI) if the assay achieves a co-efficient of variation (CV) of less than 10%. Because of current assay imprecision and concerns of over diagnosing MI, higher diagnostic thresholds are commonly employed at concentrations where the assay can achieve a CV less than 10%. We assess the relationship between plasma troponin I concentration, assay precision and clinical outcomes in patients with suspected acute coronary syndrome (ACS).
Methods and Results: Consecutive patients with suspected ACS admitted to the Royal Infirmary of Edinburgh, Scotland (n=2,092) were stratified using a sensitive troponin I assay into three groups based on the 99th percentile for plasma troponin (0.012 ng/mL; CV, 20.8%) and the diagnostic threshold (0.050 ng/mL; CV, 7.2%): <0.012, 0.012-0.049 and >0.050 ng/mL. Plasma troponin I concentrations were <0.012 ng/mL in 988 patients (47%), 0.012-0.049 ng/mL in 352 patients (17%), and >0.050 ng/mL in 752 patients (36%). At one year, patients with troponin concentrations of 0.012-0.049 ng/mL were more likely to be dead or readmitted with recurrent MI compared to those with troponin concentrations <0.012 ng/mL (13% versus 3%; OR 4.8, 95% CI 3.0-7.7; P<0.001). Compared to troponin >0.050 ng/mL, patients with troponin 0.012-0.049 ng/mL had a higher risk profile but were less likely to be diagnosed with, or investigated and treated for, ACS.
Conclusions: Lowering the diagnostic threshold to the 99th percentile and accepting greater assay imprecision would identify those at high-risk of recurrent MI and death but increase the diagnosis of MI by 46%. It remains to be established whether reclassification of these patients and treatment for MI would improve outcome.
- © 2011 by American Heart Association, Inc.