Diagnostic value of serial measurement of cardiac markers in patients with chest pain: limited value of adding myoglobin to troponin I for exclusion of myocardial infarction.
BACKGROUND
Despite improved laboratory assays for cardiac markers and a revised standard for definition of myocardial infarction (AMI), early detection of coronary ischemia in unselected patients with chest pain remains a difficult challenge.


METHODS
Rapid measurements of troponin I (TnI), creatine kinase MB (CK-MB), and myoglobin were performed in 197 consecutive patients with chest pain and a nondiagnostic electrocardiogram for AMI. The early diagnostic performances of these markers and different multimarker strategies were evaluated and compared. Diagnosis of AMI was based on European Society of Cardiology/American College of Cardiology criteria.


RESULTS
At a given specificity of 95%, TnI yielded the highest sensitivity of all markers at all time points. A TnI cutoff corresponding to the 10% coefficient of variation (0.1 microg/L) demonstrated a cumulative sensitivity of 93% with a corresponding specificity of 81% at 2 hours. The sensitivity was considerably higher compared to CK-MB and myoglobin, even considering patients with a short delay until admission. Using the 99th percentile of TnI results as a cutoff (0.07 microg/L) produced a cumulative sensitivity of 98% at 2 hours, but its usefulness was limited due to low specificities. Multimarker strategies including TnI and/or myoglobin did not provide a superior overall diagnostic performance compared to TnI using the 0.1 microg/L cutoff.


CONCLUSIONS
A TnI cutoff corresponding to the 10% coefficient of variation was most appropriate for early diagnosis of AMI. A lower TnI cutoff may be useful for very early exclusion of AMI. CK-MB and in particular myoglobin did not offer additional diagnostic value.
Department of Cardiology, Cardiothoracic Center, University Hospital, Uppsala, Sweden. kai.eggers@akademiska.se
Kai Marten
KM
Eggers
Jonas
J
Oldgren
Anna
A
Nordenskjöld
Bertil
B
Lindahl
D000368:Aged; D000789:Angina, Unstable / Q000097:blood / Q000175:diagnosis*; D015415:Biomarkers / Q000097:blood; D002637:Chest Pain / Q000097:blood*; D003402:Creatine Kinase / Q000097:blood*; D052279:Creatine Kinase, MB Form; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007527:Isoenzymes / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000097:blood / Q000175:diagnosis*; D009211:Myoglobin / Q000097:blood*; D012680:Sensitivity and Specificity; D019210:Troponin I / Q000097:blood*
D015415:Biomarkers; D007527:Isoenzymes; D009211:Myoglobin; D019210:Troponin I; D003402:Creatine Kinase; D052279:Creatine Kinase, MB Form