Whole Blood Platelet Aggregation in Chronic Kidney Disease Patients on Aspirin Study

Patients will be consented for the study and asked to initial on the consent form to state whether they agree for the genetic testing. After signing informed consent, complete medical history and medication list will be obtained and verified with the electronic medical record. After meeting all inclusion and exclusion criteria during the screening visit, those patients on aspirin for primary prevention of cardiovascular events will be asked to stop it for 2 weeks prior to blood collection for baseline data. Normal controls will be chosen after frequency matching for decade of age, gender, diabetes mellitus and interval of body mass index (5 kg/m2). Dietary supplements (Vitamin E and fish oil) known to affect platelet function will be assessed and patients on those will be asked to discontinue these. Participants with also be asked to not eat foods known to affect platelet function (coffee, chocolate, grapes, and alcohol) 48 hours prior to sample collection on visit 1. An interviewer-administered assessment of diet and exercise with a modified 24-hour dietary recall and the Stanford 7-day Physical activity Recall will be performed to ensure dietary consistency which may affect platelet aggregability on visit 1. Blood will be drawn via venopuncture for laboratory studies (whole blood platelet aggregation, von Willebrand Factor antigen levels and activity). Participants will be administered aspirin 81 mg for 2 weeks and asked to return in 2 weeks. On visit 2, whole blood platelet aggregation will be re-measured and questionnaires filled out. Two oral swabs will be taken from those participants who consented for genetic testing and samples will be stored at Dallas Veterans Affairs Medical Center for short term until shipped to Diagnostics Laboratory for genetic testing of clopidogrel cytochrome P450 polymorphisms. All participants will be administered clopidogrel 75 mg daily on top of aspirin 81 mg for 2 weeks and asked to return in 2 weeks. On visit 3, whole blood platelet aggregation will be re-measured and questionnaires filled out. At the completion of the study, participants will be placed back on their original antiplatelet agent if applicable and referred back to the primary care provider.