Department of Health Policy and Management, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
Department of Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
PLoS One. 2018 May 31;13(5):e0198132. doi: 10.1371/journal.pone.0198132. eCollection 2018.
To distinguish clinical factors that have time-varying (as opposed to constant) impact upon patient and graft survival among pediatric liver transplant recipients.
Using national data from 2002 through 2013, we examined potential clinical and demographic covariates using Gray's piecewise constant time-varying coefficients (TVC) models. For both patient and graft survival, we estimated univariable and multivariable Gray's TVC, retaining significant covariates based on backward selection. We then estimated the same specification using traditional Cox proportional hazards (PH) models and compared our findings.
For patient survival, covariates included recipient diagnosis, age, race/ethnicity, ventilator support, encephalopathy, creatinine levels, use of living donor, and donor age. Only the effects of recipient diagnosis and donor age were constant; effects of other covariates varied over time. We retained identical covariates in the graft survival model but found several differences in their impact.
The flexibility afforded by Gray's TVC estimation methods identify several covariates that do not satisfy constant proportionality assumptions of the Cox PH model. Incorporating better survival estimates is critical for improving risk prediction tools used by the transplant community to inform organ allocation decisions.
区分在儿科肝移植受者中，对患者和移植物存活具有时变（而非恒定）影响的临床因素。
利用 2002 年至 2013 年的全国数据，我们使用 Gray 的分段常数时变系数（TVC）模型检查了潜在的临床和人口统计学协变量。对于患者和移植物的存活率，我们使用单变量和多变量 Gray 的 TVC 进行了估计，根据后向选择保留有意义的协变量。然后，我们使用传统的 Cox 比例风险（PH）模型估计了相同的规格，并比较了我们的发现。
对于患者存活率，协变量包括受者诊断、年龄、种族/民族、呼吸机支持、脑病、肌酐水平、使用活体供者和供者年龄。只有受者诊断和供者年龄的影响是恒定的；其他协变量的影响随时间而变化。我们在移植物存活率模型中保留了相同的协变量，但发现它们的影响存在一些差异。
Gray 的 TVC 估计方法提供了灵活性，可以确定一些不符合 Cox PH 模型常数比例假设的协变量。纳入更好的生存估计对于改善移植界用于告知器官分配决策的风险预测工具至关重要。
