design: Genotype was determined by using first-generation DNA sequencing technology. DNA from the patients was extracted using a DNA extraction kit (TIANGEN BIOTECH, Beijing). Firstly, primers were designed for ABCB1 3435 CT, 1236 AG and 2677 AC/T. Then, the polymerase chain reaction (PCR) product was amplified and purified, and the purified PCR products were re-amplified subsequently. Finally, a ABI sequencer (Applied Biosystems, the USA) was used to sequence the amplification products.