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摘要： Objective To provide references for improving the authenticity and reliability of the retrospective study results, thus improving the quality of evidence in the real world and strengthening drug supervision and decision-making. Methods Literature review was used to study the data sources, the characteristics of retrospective research, the sources and the corrections of selective bias in the real world. Results and Conclusion The biases in retrospective study mainly come from admission rate bias, patient rate bias, survivors bias, health user bias and symptom bias.
