Studies on the Effectiveness of Warfarin for Preventing Strokes
Results from 6 clinical trials examining the effectiveness of adjusted-dose warfarin for preventing strokes in patients with atrial fibrillation.
dat.hart1999
The data frame contains the following columns:
| trial | numeric |
trial number |
| study | character |
study name (abbreviated) |
| year | numeric |
publication year |
| x1i | numeric |
number of strokes in the warfarin group |
| n1i | numeric |
number of patients in the warfarin group |
| t1i | numeric |
total person-time (in years) in the warfarin group |
| x2i | numeric |
number of strokes in the placebo/control group |
| n2i | numeric |
number of patients in the placebo/control group |
| t2i | numeric |
total person-time (in years) in the placebo/control group |
| compgrp | character |
type of comparison group (placebo or control) |
| prevtype | character |
type of prevention (primary or secondary) |
| trinr | character |
target range for the international normalized ratio (INR) |
The 6 studies provide data with respect to the number of strokes in the warfarin and the comparison (placebo or control) group. In addition, the number of patients and the total person-time (in years) is provided for the two groups. The goal of the meta-analysis was to examine the effectiveness of adjusted-dose warfarin for preventing strokes in patients with atrial fibrillation.
Hart, R. G., Benavente, O., McBride, R., & Pearce, L. A. (1999). Antithrombotic therapy to prevent stroke in patients with atrial fibrillation: A meta-analysis. Annals of Internal Medicine, 131, 492–501.
### copy data into 'dat'
dat <- dat.hart1999
### calculate log incidence rate ratios and corresponding sampling variances
dat <- escalc(measure="IRR", x1i=x1i, x2i=x2i, t1i=t1i, t2i=t2i, data=dat)
dat
### meta-analysis of log incidence rate ratios using a random-effects model
res <- rma(yi, vi, data=dat)
res
### average incidence rate ratio with 95% CI
predict(res, transf=exp)
### forest plot with extra annotations
par(mar=c(5,4,1,2))
forest(res, xlim=c(-11, 5), at=log(c(.05, .25, 1, 4)), atransf=exp,
slab=paste0(dat$study, " (", dat$year, ")"),
ilab=cbind(paste(dat$x1i, "/", dat$t1i, sep=" "),
paste(dat$x2i, "/", dat$t2i, sep=" ")),
ilab.xpos=c(-6.5,-4), cex=.85, header="Study (Year)")
op <- par(cex=.85, font=2)
text(c(-6.5,-4), 8.5, c("Warfarin", "Control"))
text(c(-6.5,-4), 7.5, c("Strokes / PT", "Strokes / PT"))
segments(x0=-8, y0=8, x1=-2.75, y1=8)
par(op)
### meta-analysis of incidence rate differences using a random-effects model
res <- rma(measure="IRD", x1i=x1i, x2i=x2i, t1i=t1i, t2i=t2i, data=dat)
resPlease choose more modern alternatives, such as Google Chrome or Mozilla Firefox.