Introduction Heart-type Fatty Acid-Binding Protein (H-FABP) has previously been assessed for early diagnosis of ACS. H-FABP has a sensitivity of 85.3% 3 to 6 h after chest pain onset.1 H-FABP (>6.48 ng/ml) has been associated with significantly increased event rates. With the introduction of highly sensitive troponin T (hsTnT), Body et al. assessed 1,171 patients with suspected cardiac chest pain using a combination of H-FABP, hsTnT and ECG to rule-out ACS with a sensitivity of 99.1% and a NPV of 99.7%.
Methodology We prospectively evaluated H-FABP in early detection of ACS. Patients admitted with cardiac chest pain within 6 h onset were recruited. Baseline demographics, cardiac risk factors and a TIMI risk score were recorded. STEMI patients were excluded. Baseline blood samples were taken for H-FABP and hsTnT. A 6 h hsTnT was taken to confirm or exclude ACS diagnosis.
ACS was denoted as chest pain with or without ECG changes and a hsTnT rise of >20% from baseline sample or a delta rise of 7 ng/l (normal <14 ng/l). We assessed if baseline H-FABP >6.32 ng/ml (99th centile, IT assay) could predict ACS.
Results We enrolled 69 patients, 45 (65%) were male. Mean age was 66.8 years. ACS was diagnosed in 23 (32.9%) patients. Mean TIMI score was 3.29 in the ACS group and 3.07 in the non-ACS group. At baseline, median H-FABP was 8.61 vs. 6.45 (p = 0.01), median baseline hsTnT was 48 vs. 9 (p < 0.001) and median repeat hsTnT was 128 vs. 9 (p < 0.001), (Table 1). Sensitivity of H-FABP was 78.3% vs. 78.3% for baseline hsTnT, with specificity 44.7% vs. 63.8%, positive predictive value (PPV) 40.9% vs. 51.4% and negative predictive value (NPV) 80.8% vs. 85.7% (Table 2). Baseline H-FABP achieved an area under curve (AUC) of 0.69 vs. 0.77 for hsTnT. H-FABP and hsTnT combined achieved an AUC of 0.71. Of note, 28 (40.5%) had a ‘triple positive’ result, 9 (13.0%) patients had a raised H-FABP/both hsTnT samples negative, of which one developed ACS within 1 year requiring emergency percutaneous coronary intervention (PCI), 2 had angiography/PCI for ongoing symptoms, 1 had normal angiography despite chest pain and 5 had further investigation including echocardiography / exercise stress testing. In addition, 2 of 23 ACS (8.7%) patients had an initial positive H-FABP / negative baseline hsTnT/positive 6 h hsTnT. Furthermore, 18 (26.1%) had a ‘triple negative’ result.
Baseline H-FABP had the same sensitivity but was less specific than hsTnT for single sample diagnosis. H-FABP has a role in early diagnosis of ACS, with a combination approach enabling identification of ACS in a select number of patients with baseline negative hsTnT/6 h positive hsTnT patients. H-FABP correctly identified 3 (33.3%) patients with both hsTnT negative results that had significant coronary disease requiring intervention.
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