Misra M, Vonesh E, Churchill D N, Moore H L, Van Stone J C, Nolph K D
Division of Nephrology, Department of Internal Medicine, and Dalton Cardiovascular Research Center, University ofMissouri-Columbia, and Dialysis Clinic, Inc., Columbia, Missouri 65212, USA.
Kidney Int. 2000 Feb;57(2):691-6. doi: 10.1046/j.1523-1755.2000.00891.x.
Residual renal function (RRF) plays an important role in dialysis patients. Studies in patients on maintenance dialysis suggest that RRF is better preserved in patients receiving peritoneal dialysis (PD) vis-à-vis those receiving hemodialysis (HD). We speculated that regardless of the patient's type of therapy, the estimate obtained for the rate of decline in glomerular filtration rate (GFR) may be biased because of informative censoring associated with patient dropout. Informative censoring occurs when patients who die or transfer to another modality very early have associated with them a lower starting GFR or a higher rate of decline of GFR than patients who either complete the study or who die or transfer much later. If patient dropout is indeed related to the rate of decline in GFR and if this relationship is ignored in the analysis, then the estimate obtained of the rate of decline in GFR may be biased.
In an attempt to determine if there is a relationship between patient dropout and the decline in GFR, we reanalyzed the CANUSA data by modeling GFR as a nonlinear function of time with the rate of decline being exponential.
This article highlights the significance of "informative censoring" when studying the decline of RRF on dialysis. The results show that for the CANUSA cohort, the mean initial GFR was significantly lower, and the rate of decline was significantly higher for patients who died or transferred to HD than for patients who were randomly censored or received a transplant. It is important to emphasize that the impact of informative censoring on previous analyses of the decline of RRF between PD versus HD is presently unclear. If bias caused by informative censoring is the same regardless of what therapy a patient is on, then conclusions from previous studies comparing the decline in GFR between PD and HD would still be valid. However, if the magnitude of the bias differs according to therapy, then additional adjustments would be needed to fairly compare the decline in GFR between PD and HD. Because this analysis is restricted to patients on PD, it would be scientifically incorrect to interpret previous studies solely on the basis of the results from this analysis.
In any longitudinal study designed to estimate trends in an outcome measured over time, it is important that the analysis of the data takes into account any effect patient dropout may have on the estimated trend. This analysis demonstrates that among PD patients, both the starting GFR and the rate of decline in GFR are associated with patient dropout. Consequently, future studies aimed at estimating the rate of decline in GFR among PD patients should also account for any dependencies between dropout and GFR. Similarly, data analyzing for apparent differences in the rate of decline of GFR between PD and HD should also adjust for possible informative censoring.
残余肾功能（RRF）在透析患者中起着重要作用。对维持性透析患者的研究表明，与接受血液透析（HD）的患者相比，接受腹膜透析（PD）的患者RRF保留得更好。我们推测，无论患者的治疗方式如何，由于与患者退出相关的信息性删失，肾小球滤过率（GFR）下降速率的估计值可能存在偏差。当过早死亡或转至其他治疗方式的患者与完成研究或较晚死亡或转至其他治疗方式的患者相比，起始GFR较低或GFR下降速率较高时，就会出现信息性删失。如果患者退出确实与GFR下降速率相关，而在分析中忽略这种关系，那么所得到的GFR下降速率估计值可能存在偏差。
为了确定患者退出与GFR下降之间是否存在关系，我们通过将GFR建模为时间的非线性函数（下降速率呈指数形式），对CANUSA数据进行了重新分析。
本文强调了在研究透析时RRF下降情况时“信息性删失”的重要性。结果显示，对于CANUSA队列，死亡或转至HD的患者的平均初始GFR显著更低，且下降速率显著高于随机删失或接受移植的患者。需要强调的是，目前尚不清楚信息性删失对先前关于PD与HD之间RRF下降分析的影响。如果信息性删失导致的偏差无论患者接受何种治疗都是相同的，那么先前比较PD和HD之间GFR下降情况的研究得出的结论仍然有效。然而，如果偏差的大小因治疗方式而异，那么就需要进行额外的调整，以便公平地比较PD和HD之间GFR的下降情况。由于本分析仅限于PD患者，仅根据本分析结果来解释先前的研究在科学上是不正确的。
在任何旨在估计随时间测量的结局趋势的纵向研究中，重要的是数据分析要考虑到患者退出可能对估计趋势产生的任何影响。本分析表明，在PD患者中，起始GFR和GFR下降速率均与患者退出相关。因此，未来旨在估计PD患者中GFR下降速率的研究也应考虑退出与GFR之间的任何相关性。同样，分析PD和HD之间GFR下降速率的明显差异的数据也应针对可能的信息性删失进行调整。
