Carides G W, Heyse J F, Iglewicz B
Merck Research Laboratories, 10 Sentry Parkway, BL 2-3, Blue Bell, PA 19422, USA.
Biostatistics. 2000 Sep;1(3):299-313. doi: 10.1093/biostatistics/1.3.299.
In many clinical trials and evaluations using medical care administrative databases it is of interest to estimate not only the survival time of a given treatment modality but also the total associated cost. The most widely used estimator for data subject to censoring is the Kaplan-Meier (KM) or product-limit (PL) estimator. The optimality properties of this estimator applied to time-to-event data (consistency, etc.) under the assumptions of random censorship have been established. However, whenever the relationship between cost and survival time includes an error term to account for random differences among patients' costs, the dependency between cumulative treatment cost at the time of censoring and at the survival time results in KM giving biased estimates. A similar phenomenon has previously been noted in the context of estimating quality-adjusted survival time. We propose an estimator for mean cost which exploits the underlying relationship between total treatment cost and survival time. The proposed method utilizes either parametric or nonparametric regression to estimate this relationship and is consistent when this relationship is consistently estimated. We then present simulation results which illustrate the gain in finite-sample efficiency when compared with another recently proposed estimator. The methods are then applied to the estimation of mean cost for two studies where right-censoring was present. The first is the heart failure clinical trial Studies of Left Ventricular Dysfunction (SOLVD). The second is a Health Maintenance Organization (HMO) database study of the cost of ulcer treatment.
在许多使用医疗管理数据库的临床试验和评估中，不仅估计给定治疗方式的生存时间，而且估计与之相关的总成本都很重要。对于受删失影响的数据，最广泛使用的估计器是Kaplan-Meier（KM）或乘积限（PL）估计器。在随机删失的假设下，应用于事件发生时间数据的该估计器的最优性质（一致性等）已经得到确立。然而，只要成本与生存时间之间的关系包含一个误差项以解释患者成本之间的随机差异，删失时的累积治疗成本与生存时间时的累积治疗成本之间的相关性就会导致KM给出有偏差的估计。在估计质量调整生存时间的背景下，此前也曾注意到类似现象。我们提出一种平均成本估计器，它利用了总治疗成本与生存时间之间的潜在关系。所提出的方法利用参数或非参数回归来估计这种关系，并且当这种关系被一致估计时是一致的。然后我们给出模拟结果，这些结果说明了与另一种最近提出的估计器相比在有限样本效率方面的提升。然后将这些方法应用于对两项存在右删失的研究的平均成本估计。第一项是心力衰竭临床试验左心室功能障碍研究（SOLVD）。第二项是一项关于溃疡治疗成本的健康维护组织（HMO）数据库研究。
