Assessment of a heart-type fatty acid-binding protein test in the prehospital diagnosis of acute myocardial infarction

Objective: To assess the usefulness of testing for heart-type fatty acid-binding protein (h-FABP) to obtain complementary information for the diagnosis of acute myocardial infarction (AMI) in the prehospital setting, particularly in patients whose symptoms began less than 3 hours earlier. Methods: Prospective cross-sectional study in patients with probable AMI attended by 3 advanced life support units belonging to the health service of Castile-La Mancha, Spain. The recorded variables were clinical and epidemiologic data, electrocardiograms, and the results of a rapid h-FABP test. The patients were followed while in hospital, and the definitive diagnosis was considered to be the one eventually made in hospital. Indices reflecting the diagnostic yield of the test were calculated. Results: Seventy-three patients were tested. The h-FABP test had to be repeated for 21 patients because of problems related to storage of the strips or interpreting the results, and in 7 cases (9.6%) test results were judged unusable. In 50 of the 66 patients for whom readable h-FABP results were obtained, the test was done within 3 hours of the onset of symptoms. In this group, the h-FABP test achieved a sensitivity of 91% (95% confidence interval [CI]), 76%-98%), specificity of 37% (95% CI, 15%-65%), efficiency of 74% (95% CI, 64%-85%), positive predictive value of 76% (95% CI, 60%-88%), and negative predictive value of 67% (95% CI, 30%-93%). The specificity of the h-FABP test was higher when calculated for the entire patient sample regardless of time elapsed since the onset of symptoms, but the other indices were similar. The diagnostic yield of the test was lower in patients with atypical clinical pictures and/or electrocardiograms than in those with more characteristic signs and symptoms. Conclusion: The h-FABP test result does not help make a prehospital diagnosis of AMI when symptoms have started less than 3 hours before the patient reaches the hospital, and the diagnostic yield of the test is particularly low in cases in which the clinical picture is nuclear. [Emergencias 2009;21:333-338]