Platelet Function Test Interactions

High-dose vitamin E (alpha-tocopherol above 400 IU per day) inhibits platelet aggregation through a protein kinase C-dependent mechanism, producing prolonged bleeding times and abnormal results on platelet function analyzers (such as PFA-100, VerifyNow, and light transmission aggregometry). The effect is most pronounced when vitamin E is combined with aspirin or other antiplatelet agents and can interfere with workup for bleeding disorders.