metafor (version 1.9-2)

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: lll{ 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) }

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
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.hart1999)
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
forest(res, xlim=c(-14, 6), at=log(c(.05, .25, 1, 4)), atransf=exp, 
       slab=paste(dat$study, "(", dat$year, ")", sep=""), 
       ilab=cbind(paste(dat$x1i, "/", dat$t1i, sep=""), 
       paste(dat$x2i, "/", dat$t2i, sep="")), 
       ilab.xpos=c(-8,-5), cex=.85)
op <- par(cex=.85, font=2)
text(-14, 7.5, "Study (Year)", pos=4)
text(6,   7.5, "IRR [95% CI]", pos=2)
text(c(-8,-5), 8.0, c("Strokes /", "Strokes /"))
text(c(-8,-5), 7.5, c("Person-Time", "Person-Time"))
text(c(-8,-5), 8.5, c("Warfarin", "Control"))
segments(x0=-9, y0=8.25, x1=-4, y1=8.25)
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.hart1999)
res