Clinical Research Directory

Inclusion Criteria: * Age 18 years or older * Able to consent to study Exclusion Criteria from entire study * Primary hemostasis diagnosis * Von Willebrand Disease * Bernard-Soulier syndrome * Glanzmann thrombasthenia * Idiopathic thrombocytopenic purpura * Drug-induced thrombocytopenia * Heparin-induced thrombocytopenia * Thrombotic thrombocytopenic purpura * Hemolytic uremic syndrome * Participant is on anticoagulant therapy * Specifically thienopyrdines \[Ticlopidine, Clopidogrel\] and GPIIb/IIIa inhibitors \[ReoPro, Aggrastat, Integrilin\] * Participant is on medication that contains ASA or aspirin (see list below in Study Procedure) * Participant is on nonsteroidal anti-inflammatory agents that are known to induce temporary platelet dysfunction (see list below in Study Procedure) * Participant is on non-prescription medications containing aspirin (see list below in Study Procedure) * PFA-100 result falls outside of reference interval listed in the package insert (suggested criteria in the PFA-100 Evaluation Protocol as described in the PFA-100 System: Getting Started Guide) * If hematocrit is less than 35% * If platelets are less than 150 x10\^3/uL Exclusion Criteria from Cohort B but not Cohort A * Potential for adverse reactions between current medication and aspirin as dictated by staff pharmacist * Allergy to ASA or aspirin * Previous allergic reaction to ASA or aspirin * Participant is pregnant * Asthma, or history of, with nasal polyps and rhinitis * Stomach ulcers or bleeding * Severe kidney disease * Severe liver disease * Hemophilia * Pregnant or breast feeding