[英]Obtain the baseline hazard function/survival function from an extended Cox model (with external time-dependent covariates)
[英]C-statistics and 95% confidence interval for Cox-model with time-dependent covariates
我正在執行與時間相關的協變量的Cox回歸。 我對計算Concordance指數的95%置信區間特別感興趣。 但是,coxph模型的標准摘要僅返回Concordance索引及其標准誤差。 是否有可能獲得95%的CI?
謝謝!
library(survival)
temp <- subset(pbc, id <= 312, select=c(id:sex, stage))
pbc2 <- tmerge(temp, temp, id=id, death = event(time, status)) #set range
pbc2 <- tmerge(pbc2, pbcseq, id=id, ascites = tdc(day, ascites),
bili = tdc(day, bili), albumin = tdc(day, albumin),
protime = tdc(day, protime), alk.phos = tdc(day, alk.phos))
fit2 <- coxph(Surv(tstart, tstop, death==2) ~ log(bili) + log(protime), pbc2)
summary(fit2)
coxph(formula = Surv(tstart, tstop, death == 2) ~ log(bili) +
log(protime), data = pbc2)
n= 1807, number of events= 125
coef exp(coef) se(coef) z Pr(>|z|)
log(bili) 1.24121 3.45981 0.09697 12.800 <2e-16 ***
log(protime) 3.98340 53.69929 0.43589 9.139 <2e-16 ***
---
Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
exp(coef) exp(-coef) lower .95 upper .95
log(bili) 3.46 0.28903 2.861 4.184
log(protime) 53.70 0.01862 22.853 126.181
**Concordance= 0.886 (se = 0.029 )**
Rsquare= 0.168 (max possible= 0.508 )
Likelihood ratio test= 332.1 on 2 df, p=<2e-16
Wald test = 263.3 on 2 df, p=<2e-16
Score (logrank) test = 467.8 on 2 df, p=<2e-16
使用自舉程序中的RMS軟件包中的驗證功能是否有意義,以便使用引導程序為C索引獲取95%的CI? 我想出了以下代碼。 你怎么看? 但是,我不確定如何正確地處理來自訓練/測試列的Dxy值(訓練的CI對我而言似乎不錯,而來自測試列的CI看起來非常狹窄)。
library(survival)
library(rms)
library(tidyboot)
temp <- subset(pbc, id <= 312, select=c(id:sex, stage))
pbc2 <- tmerge(temp, temp, id=id, death = event(time, status)) #set range
pbc2 <- tmerge(pbc2, pbcseq, id=id, ascites = tdc(day, ascites),
bili = tdc(day, bili), albumin = tdc(day, albumin),
protime = tdc(day, protime), alk.phos = tdc(day, alk.phos))
fit2 <- cph(Surv(tstart, tstop, death==2) ~ log(bili) + log(protime), pbc2, x=T, y=T, surv=T)
set.seed(1)
output <- capture.output(validate(fit2, method="boot", B=1000, dxy=T, pr =T))
head(output)
output <- as.matrix(output)
output_dxy <- as.matrix(output[grep('^Dxy', output[,1]),])
output_dxy <- gsub("(?<=[\\s])\\s*|^\\s+|\\s+$", "", output_dxy, perl=TRUE)
train <- abs(as.numeric(lapply(strsplit(output_dxy, split=" "), "[", 2))[1:1000])/2+0.5
test <- abs(as.numeric(lapply(strsplit(output_dxy, split=" "), "[", 3))[1:1000])/2+0.5
summary(train)
summary(test)
ci_lower(train, na.rm = FALSE)
ci_upper(train, na.rm = FALSE)
ci_lower(test, na.rm = FALSE)
ci_upper(test, na.rm = FALSE)
順便說一句,在log bili和log protime中,這種關系不太可能是線性的。 日志中的樣條函數是保證的。
在使用0.886的一致性概率估計值之前,您需要從R survival
包中進行驗證,
如果這兩個條件都滿足,則可以使用+1.96 se得出c指數的大約 0.95置信區間。
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