Crc is the resident coordinator of the clinical center, responsible for the management of patients' visits, the handling of adverse events, the input or transcription of information, the management of documents, the management of drug flow and the management of experimental materials. The main purpose of adopting crc is to reduce the workload of researchers, thus improving their enthusiasm, improving the efficiency of testing and reducing the probability of mistakes. Crc can be equipped or not according to the actual situation of each center.