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A Methodology for the Health Sciences - part 9

Nguy cơ tương đối tức thời của LMCA 70% so với 0 LMCA% là gì? Hãy xem xét ba bệnh nhân với các giá trị covariate được đưa ra trong Bảng 16,18. Theo các giá trị trung bình của các dữ liệu, một và sự sống còn hai năm là 88,0% và 80,16%, tương ứng. | PROBLEMS 705 Table 16.18 Variable Data for Problem 16.11 Variable Patient Number 1 2 3 Impairment Severe Mild Moderate Age 64 51 59 lMca 50 0 0 EF 15 32 23 Digitalis Yes Yes Yes Therapy Medical Surgical Medical Vessel 3 2 3 c What is the instantaneous relative risk of 70 LMCA compared to 0 LMCA d Consider three patients with the covariate values given in Table 16.18. At the mean values of the data the one- and two-year survival were 88.0 and 80.16 respectively. Find the probability of one- and two-year survival for these three patients. e With this model i Can surgery be better for one person and medical treatment for another Why What does this say about unthinking application of the model ii Under surgical therapy can the curve cross over the estimated medical survival for some patients For heavy surgical mortality would a proportional hazard model always seem appropriate 16.12 The Clark et al. 1971 heart transplant data were collected as follows. People with failing hearts waited for a donor heart to become available this usually occurred within 90 days. However some patients died before a donor heart became available. Figure 16.19 plots the survival curves of 1 those not transplanted indicated by circles and 2 the transplant patients from time of surgery indicated by the triangles . Figure 16.19 Survival calculated by the life table method. Survival for transplanted patients is calculated from the time of operation survival of nontransplanted patients is calculated from the time of selection for transplantation. 706 ANALYSIS OF THE TIME TO AN EVENT SURVIVAL ANALYSIS a Is the survival of the nontransplanted patients a reasonable estimate of the nonoperative survival of candidates for heart transplant Why or why not b Would you be willing to conclude from the figure assuming a statistically significant result that 1960s heart transplant surgery prolonged life Why or why not c Consider a Cox model fitted with transplantation as a time-dependent covariate hi t h0 t