纵向研究存在的问题：乳腺癌患者案例分析

Although this study used longitudinal data, there are still the following problems: 1. Our patients are all female patients with breast cancer, so our research results are not applicable to other cancers or males. 2. In the collection of retest data, the number of collected retest data is small, and a small sample size may cause the results to be affected by random errors, making it difficult to accurately reflect the true situation of the measured variables. This makes the results may only be applicable to specific samples or situations and cannot be generalized to the entire target population. 3. In the first data collection, patients answered the EQ-5D-5L questionnaire first, which may have a certain impact on patients' responses to the QLQ-C30, as EQ-5D-5L mainly focuses on health status itself and may introduce certain biases in patients' attention and evaluation methods when answering the QLQ-C30. Patients may pay more attention to their own health conditions and overlook other aspects of quality of life assessment.