Research: BAUSSELL and colleagues,

Listed in Issue 108


BAUSSELL and colleagues, University of Maryland School of Nursing, Baltimore, MD 21201, USA,, have found that larger effect sizes are correlated with better quality in controlled trials of complementary and alternative medicine.


The aim of the study was to determine if the quality of complementary and alternative medicine (CAM) placebo controlled randomized controlled trials is related to the effect sizes they produce.


A sample of 25 CAM meta-analyses was identified containing published effect sizes for at least three efficacy trials employing placebo control groups. From these 25 reviews, 26 pairs of trials were selected: the one reporting the largest effect size and the matching trial reporting the smallest effect size. Quality and publication characteristics were then abstracted from each trial.


The study found that trials possessing the largest effect sizes within a meta-analysis were also associated with higher quality ratings than their counterparts possessing the lowest effect sizes (P=.019). This is in contrast to previously published analyses of these correlations.


Possible theoretical reasons for this unexpected positive relationship include (a) sampling errors, (b) reduced within-group variations, (c) fraudulent reporting, and (d) the restriction of the analyses to placebo controlled trials.


Bausell RB, Lee WL, Soeken KL, Li YF, Berman BM. Larger effect sizes were associated with higher quality ratings in complementary and alternative medicine randomized controlled trials. Journal of Clinical Epidemiology 57(5): 438-446, May 2004.


This is good news and should be an incentive to all researchers in CAM to carefully quality-control their trials!

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