Sample size re-estimation is essential in oncology studies. However, the use of blinded sample size reassessment for survival data has been rarely reported. Based on the density function of the exponential distributio...Sample size re-estimation is essential in oncology studies. However, the use of blinded sample size reassessment for survival data has been rarely reported. Based on the density function of the exponential distribution, an expectation-maximization（EM） algorithm of the hazard ratio was derived, and several simulation studies were used to verify its applications. The method had obvious variation in the hazard ratio estimates and overestimation for the relatively small hazard ratios. Our studies showed that the stability of the EM estimation results directly correlated with the sample size, the convergence of the EM algorithm was impacted by the initial values, and a balanced design produced the best estimates. No reliable blinded sample size re-estimation inference can be made in our studies, but the results provide useful information to steer the practitioners in this field from repeating the same endeavor.展开更多
Traumatic tricuspid valve insufficiency (TTVI) is a relatively uncommon disease. To summarize the experience in the diagnosis and treatment of TTVI, we have analyzed the clinical data of 3 patients with TTVI who were ...Traumatic tricuspid valve insufficiency (TTVI) is a relatively uncommon disease. To summarize the experience in the diagnosis and treatment of TTVI, we have analyzed the clinical data of 3 patients with TTVI who were admitted to the department of cardiac surgery of our hospital between April 1997 to April 2002. Relevant literatures have also been reviewed.展开更多
基金supported by the National Natural Science Foundation of China(81273184)the National Natural Science Foundation of China Grant for Young Scientists (81302512)
文摘Sample size re-estimation is essential in oncology studies. However, the use of blinded sample size reassessment for survival data has been rarely reported. Based on the density function of the exponential distribution, an expectation-maximization（EM） algorithm of the hazard ratio was derived, and several simulation studies were used to verify its applications. The method had obvious variation in the hazard ratio estimates and overestimation for the relatively small hazard ratios. Our studies showed that the stability of the EM estimation results directly correlated with the sample size, the convergence of the EM algorithm was impacted by the initial values, and a balanced design produced the best estimates. No reliable blinded sample size re-estimation inference can be made in our studies, but the results provide useful information to steer the practitioners in this field from repeating the same endeavor.
文摘Traumatic tricuspid valve insufficiency (TTVI) is a relatively uncommon disease. To summarize the experience in the diagnosis and treatment of TTVI, we have analyzed the clinical data of 3 patients with TTVI who were admitted to the department of cardiac surgery of our hospital between April 1997 to April 2002. Relevant literatures have also been reviewed.
