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Highly precise laboratory methods have been developed to determine cardiac troponin levels (cTn) according to the universal definition of acute myocardial infarction (MI). We examined the impact of lowering the level of detection of cTn measurement in consecutive patients presenting to the emergency department (ED) of a large German community hospital.
cTnT levels were measured using a standard assay (Roche cTnT fourth generation; cutoff ≥0.04 ng/ml) and a high-sensitive assay (Roche cTnThs; cutoff ≥0.014 ng/ml). Patients were categorized to have an acute MI according to the universal definition using the old or the new cutoff point of cTnT levels (cTnT ≥0.04 ng/ml or cTnThs ≥0.014 ng/ml).
We analyzed 137 consecutive patients with chest pain admitted to the ED (age: 65.7 ± 15.5 years; 63.5% male; in-hospital mortality: 0.7%). Totals of 36%, 22% and 42% of patients presented within 2 hours, 2 to 6 hours and >6 hours of chest pain. Using the old cutoff point, 30 patients have been classified as acute MI (type 1 MI: 67%; type 2 MI: 33%). Using the new cutoff point (TnThs ≥0.014 μg/l), diagnosis of acute MI significantly increased by 116% (n = 65; type 1 MI: 54%; type 2 MI: 46%; P < 0.05). Type 1 MI increased by 75%, which was reflected by a 57% decrease of patients formerly classified as instable angina. Of note, increases of MI diagnosis were mainly reflected by a 200% increase of type 2 MI (for example, acute heart failure, tachycardia or hypertensive crisis). Numbers of patients with noncardiac chest pain were not significantly changed with the use of the new cutoff point. AUC of admission cTnT levels were 0.76 and 0.96 for the cTnT fourth generation and cTnThs (P < 0.05). At admission, sensitivity and specificity of cTnThs were 93% and 94% for the detection of acute MI, while they were 32% and 96% using cTnT fourth generation.
Using lower cutoff points for the definition of MI as suggested by current recommendations, the rate of chest pain patients with acute MI doubled. Because the increased rate of patients categorized as acute MI is mainly reflected MI type 2, the ED triage decision at lower cutoff levels of cTnT levels should include patient history, physical examination, 12-lead ECG and cardiac imaging.