ObjectivesAntiplatelet therapy is prevalent and can potentiate bleeding complications associated with trauma and surgery. Laboratory identification and quantification of the effect of antiplatelet medications has been difficult, with several assays, including the Platelet Function Assay [PFA]-100, yielding inconclusive results. The purpose of this study was to evaluate the effectiveness of thromboelastography with platelet mapping (TEG-PM) to identify the presence of antiplatelet medications and compare these results with the PFA-100. MethodsAll trauma patients with TEG-PM studies from September 2013 to September 2014 were retrospectively collected. The medical records were reviewed to determine home antiplatelet medications. Patients were then evaluated for concurrent PFA-100 tests to allow direct comparison of the studies. ResultsTwenty-one patients had both TEG-PM and PFA-100 test performed. In this set of patients, the sensitivity and specificity of the PFA for detecting antiplatelet medications was 50.0% and 61.9%, respectively; the TEG-PM had 88.9% sensitivity and 41.7% specificity for detecting aspirin and 100% sensitivity and 8.3% specificity for detecting clopidogrel. ConclusionThromboelastography with platelet mapping was more sensitive for detecting both aspirin and clopidogrel than the PFA-100; the 100% sensitivity in detecting clopidogrel is key and indicates this may be a useful screening tool to rule out clopidogrel use in trauma patients. Interestingly, there is a very low specificity, which may be related to acute traumatic coagulopathy.