Data from a trial of usrodeoxycholic acid

Description

Data from a trial of ursodeoxycholic acid (UDCA) in patients with primary biliary cirrohosis (PBC).

Usage

data("udca")

Format

A data frame with 170 observations on the following 15 variables.

id

subject identifier

trt

treatment of 0=placebo, 1=UDCA

entry.dt

date of entry into the study

last.dt

date of last on-study visit

stage

stage of disease

bili

bilirubin value at entry

riskscore

the Mayo PBC risk score at entry

death.dt

date of death

tx.dt

date of liver transplant

hprogress.dt

date of histologic progression

varices.dt

appearance of esphogeal varices

ascites.dt

appearance of ascites

enceph.dt

appearance of encephalopathy

double.dt

doubling of initial bilirubin

worsen.dt

worsening of symptoms by two stages

Details

This data set is used in the Therneau and Grambsh. The udca1 data set contains the baseline variables along with the time until the first endpoint (any of death, transplant, ..., worsening). The udca2 data set treats all of the endpoints as parallel events and has a stratum for each.

References

T. M. Therneau and P. M. Grambsch, Modeling survival data: extending the Cox model. Springer, 2000.

K. D. Lindor, E. R. Dickson, W. P Baldus, R.A. Jorgensen, J. Ludwig, P. A. Murtaugh, J. M. Harrison, R. H. Weisner, M. L. Anderson, S. M. Lange, G. LeSage, S. S. Rossi and A. F. Hofman. Ursodeoxycholic acid in the treatment of primary biliary cirrhosis. Gastroenterology, 106:1284-1290, 1994.

Examples

data(udca)
# values found in table 8.3 of the book
fit1 <- coxph(Surv(futime, status) ~ trt + log(bili) + stage +
          cluster(id), data=udca1)
fit2 <- coxph(Surv(futime, status) ~ trt + log(bili) + stage +
          cluster(id) + strata(endpoint), data=udca2)