OBJECTIVES: Chest pain is one of the most common complaints among patients admitted to emergency departments. Cardiac troponins, CK-MB and myoglobin, which are used routinely in the diagnosis of acute coronary syndrome (ACS), are not elevated in the initial hours of ACS--precluding their usefulness in the early diagnosis. The aim of this study is to determine the efficacy of H-FABP compared to myoglobin and CK-MB in the early diagnosis of ACS. METHODS: Sixty-seven patients with ACS were enrolled in the study. An initial blood sample was obtained for CK-MB, cTnT, myoglobin and H-FABP. At the fourth, eighth, and 12th hours, repeat ECGs and cardiac enzyme samples were obtained. H-FABP test was repeated at the fourth hour. RESULTS: H-FABP has sensitivity equal to that of CK-MB and superior to that of myoglobin (97.6%, 96.7%, 85.4%, respectively) on the first hour. This trend extends to the fourth hour of myocardial injury as well. H-FABP was more specific than CK-MB, myoglobin and troponin T at the first hour (38.5%, 34.6%, 34.6%, 23.1%, respectively), whereas its specificity at the fourth hour was equal to those of CK-MB and troponin T and exceeded that of myoglobin. CONCLUSIONS: It can be suggested that in patients with an initial diagnosis of ACS and within 20 hours from symptom onset, H-FABP levels may be measured. For this purpose, point-of-care H-FABP test may be utilized, which has the advantage of bedside testing and rapid test results