Genotyping
Frequently occurring genetic polymorphisms tied to aspirin and clopidogrel resistance were prioritized (detailed in Table 1 ). Genomic DNA from leukocytes in blood was extracted using the EZNA™ Blood DNA Midi Kit (Omega Bio-Tek, Norcross, GA, USA). Genotyping was performed by Boao Biotechnology Co., Ltd (Beijing, China) by MALDI-TOF mass spectrometry using the MassARRAY system (Sequenom, San Diego, CA, USA) according to the manufacturer’s instructions. Sequenom Assay Design 3.1 software (Sequenom, San Diego, CA, USA) was used to design single-base extensions and PCR primers. Genotype calling was performed in real-time using MassARRAY RT software version 3.0.0.4 and analyzed using MassARRAY Typer software version 3.4 (Sequenom, San Diego, CA, USA). The analysis was repeated for quality control on randomly selected subgroups of 10% of cases and controls; reproducibility was 100%.