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Myoglobin in the early evaluation of acute chest pain
1Department of Pathology, Penrose Hospital, Colorado Springs 80907, USA.
Insights
Serial myoglobin testing aids in diagnosing acute myocardial infarction (AMI). A 100% negative predictive value after two hours helps rule out AMI, improving emergency department patient triage.
Area of Science:
- Cardiology
- Emergency Medicine
- Biomarker Research
Background:
- Many patients hospitalized for suspected acute myocardial infarction (AMI) receive non-AMI diagnoses.
- A significant percentage of AMI patients are discharged inappropriately.
- Myoglobin rises early (2-3 hours) after myocardial injury.
Purpose of the Study:
- To evaluate the diagnostic utility of myoglobin in patients presenting with acute chest pain.
- To assess myoglobin's role in the early detection and exclusion of AMI.
Main Methods:
- Serial blood samples collected from 89 suspected AMI patients in the emergency department.
- Analysis included myoglobin, creatine kinase (CK), and creatine kinase isoenzyme (CK-MB).
- Diagnosis of AMI confirmed in 28% of patients.
Main Results:
- Myoglobin sensitivity for AMI detection was 56% on admission, increasing to 100% at 2 hours.
- 52% of AMI patients showed elevated myoglobin before CK or CK-MB changes.
- Negative predictive value for myoglobin was 83% on admission, reaching 100% at 2 hours.
Conclusions:
- Serial myoglobin testing demonstrates high sensitivity and negative predictive value for AMI.
- Early myoglobin assessment can aid in the accurate triage of acute chest pain patients.
- A 100% negative predictive value at 2 hours is crucial for excluding AMI.
Abstract:
Two thirds of patients hospitalized to rule out acute myocardial infarction (AMI) are eventually found to have a non-AMI diagnosis, whereas 2% to 8% of patients with AMI are inappropriately discharged from the emergency department. Myoglobin has been shown to increase within 2 to 3 hours of myocardial injury. This study evaluates the usefulness of myoglobin in acute chest pain. Serial blood samples were obtained from 89 suspected AMI patients evaluated in the emergency department. Testing included creatine kinase (CK), a creatine kinase isoenzyme (CK-MB), and myoglobin. Twenty five of 89 patients (28%) had a diagnosis of AMI. The sensitivity of myoglobin for the detection of AMI was 56% at the time of admission and 100% 2 hours after admission. Thirteen of 25 AMI patients (52%) had a positive myoglobin before increases in CK or CK-MB, including one patient discharged from the emergency department. More importantly, the negative predictive value for myoglobin at the time of admission was 83% and was 100% two hours after admission. This potential for 100% predictability in excluding AMI by the use of serial myoglobin determinations will be very helpful in the correct triage of patients presenting with acute chest pain.