metafor (version 1.9-9)

dat.hart1999: Studies on the Effectiveness of Warfarin for Preventing Strokes

Description

Results from 6 clinical trials examining the effectiveness of adjusted-dose warfarin for preventing strokes in patients with atrial fibrillation.

Usage

dat.hart1999

Format

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)	trial

Source

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.

Details

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.

Examples

### load data
dat <- get(data(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)
op <- par(cex=.85, font=2)
text(-11, 7.5, "Study (Year)", pos=4)
text(  5, 7.5, "IRR [95% CI]", pos=2)
text(c(-6.5,-4), 8.0, c("Warfarin", "Control"))
text(c(-6.5,-4), 7.5, c("Strokes / PT", "Strokes / PT"))
segments(x0=-7.75, y0=7.75, x1=-2.75, y1=7.75)
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)
res