Evaluating possible acute coronary syndrome in primary care: the value of signs, symptoms, and plasma heart-type fatty acid-binding protein (H-FABP). A diagnostic study

BACKGROUND: Additional diagnostic means could be of added value when evaluating possible acute coronary syndrome (ACS) in primary care. AIM: To determine whether heart-type fatty acid-binding protein (H-FABP)-based point-of-care (POC) biomarker testing, embedded in a clinical decision rule (CDR), is helpful to the GP when evaluating possible ACS. DESIGN & SETTING: A prospective, non-randomised, double-blinded, diagnostic derivation study was undertaken, with a delayed-type cross-sectional diagnostic model among GPs in the Netherlands and Belgium. METHOD: Signs and symptoms predicting acute myocardial infarction (AMI) or ACS were identified using both logistic regression analysis, and classification and regression trees (CART). Diagnostic values of the POC H-FABP test (cut-off value 4 ng/ml) alone and as part of a CDR were determined. RESULTS: A total of 303 participants (48.8% male) with chest pain or discomfort who had consulted a GP were enrolled. ACS was found in 32 (10.6%) of these 303 patients. For ACS, sensitivity and negative predictive value (NPV) of the POC H-FABP test was 25.8% (95% confidence interval [CI] = 12.5 to 44.9) and 91.6% (95% CI = 87.6% to 94.5%), respectively. The area under the receiver operating curve of the optimal CDR was 0.78 for ACS. CONCLUSION: Sensitivity of the current H-FABP POC test (cut-off value 4 ng/ml) as a stand-alone test is poor, either owing to limitations of the marker or of the test device. Usability of a CDR derived from these results is doubtful: the number of ACS cases missed by the GP is reduced but, as a consequence, disproportionally more ACS-negative patients are referred.