Diagnostic value of heart fatty acid binding protein and myoglobin in patients admitted with chest pain

Introduction Patients presenting with chest pain do so at varying times following its onset. In addition, their histories can be unreliable, making the interpretation of time-dependent biochemical markers difficult. Patients are therefore subsequently managed according to measurements of specific markers, such as troponin, taken many hours following their admission. Earlier markers such as myoglobin and heart fatty acid binding protein (hFABP) may provide information earlier; however, the true role of such markers remains unclear when applied to real life patient cohorts. We aimed to evaluate and compare the diagnostic accuracy of the early markers hFABP and myoglobin (in terms of area under ROC curves, sensitivity and specificity) to troponin I (cTnI) in a pragmatic group of patients presenting with chest pain. Methods 302 patients presenting with chest pain had blood samples withdrawn both on admission and 12 h later. These were analysed for cTnI, myoglobin and hFABP. Standard clinical and electrocardiographic data were also obtained. Only the cTnI results were reported back to the clinicians and hence only they would have affected clinical care. Patients were grouped clinically according to both the American College of Cardiology/European Society of Cardiology new definition of myocardial infarction (MI) and by clinicians' diagnosis of MI. Results Median time from onset of symptoms to admission was 5.0 h (IQR 3.0-12 h). Greater ROC curve areas for the diagnosis of MI by both sets of criteria were obtained for cTnI over both myoglobin and hFABP. ROC curve areas for myoglobin and hFABP were also no better than that for cTnI in those patients presenting less than 4 h after the onset of chest pain. Both myoglobin and hFABP also performed poorly in those patients who were cTnI negative on admission. Conclusion Myoglobin and hFABP provide little clinical value when measured on admission in patients presenting with chest pain.