Abstract: An application of an ABCC3-013 mRNA splicing variant for manufacturing a testing kit for clopidogrel resistance is provided. Part of the nucleotide sequences of the ABCC3-013 mRNA is described as SEQ ID No. 2. The test kit can measure an in vivo (such as peripheral leukocytes) expression levels of the ABCC3-013 mRNA of a patient to determine clopidogrel resistance, thereby providing a new method for diagnostics of clopidogrel resistance, which would help guide personalized therapy of clopidogrel in patient care. An all new test kit is provided for assay of clopidogrel resistance, characterized by an AUC of 0.674 (P=0.0018), a sensitivity of 52%, and a specificity of 86% for its performance in clinical settings, all of which are significantly improved compared with CYP2C19 genotyping that is recommended by US FDA and CPIC for the same purpose.