The authors of the recent meta-analysis(1)on the management of
chronic illness need to be commended for their efforts. They have
generated evidence on the effectiveness of different disease management
programmes, which no doubt will be of interest to patients, and providers
of care. However, I was surprised to find that language bias has not been
addressed by the authors.
It has been shown(2) that authors are more likely to publish
randomised controlled trials (RCTs) in an English-language journal if the
results are significant. Hence, English language bias may be introduced in
reviews and meta-analyses if they include only trials reported in English.
There is mixed evidence on the impact of performing meta-analysis leaving
out papers published in languages other than English. Gregoire et al
(3)found that for 1 in 36 meta-analyses results and conclusions differed
when non-English papers were included in reanalysis. According to Juni et
al (4) excluding trials published in languages other than English
generally has little effect on summary treatment effect estimates but it
would be hard to predict the impact on individual systematic reviews.
I performed a quick search of Medline selecting all the non-English
languages and used the key words utilised by the authors in their search.
There were over 100 hits in the six different languages although it is not
known how many of these might be relevant. BMJ, which has published papers
on investigating (5)bias in meta-analysis, should have paid more attention
to the language bias in the discussion section of this publication.
References
1)Weingarten SR, Henning JM, Badamgarav E, Knight K, Hasselblad V, et
al. Interventions used in disease management programmes for patients with
chronic illness-which ones work? Meta-analysis of published reports. BMJ
2002;325:925.
2)Egger M, Zellweger-Zahner T, Schneider M, Junker C, Lengeler C,
Antes G. Language bias in randomised controlled trials published in
English and German. Lancet 1997;350(9074):326-9.
3)Gregoire G, Derderian F, Le Lorier J. Selecting the language of the
publications included in a meta-analysis: is there a Tower of Babel bias?
J Clin Epidemiol 1995;48(1):159-63.
4)Juni P, Holenstein F, Sterne J, Bartlett C, Egger M. Direction and
impact of language bias in meta-analyses of controlled trials: empirical
study. Int J Epidemiol 2002;31(1):115-23.
5)Sterne JA, Egger M, Smith GD. Systematic reviews in health care:
Investigating and dealing with publication and other biases in meta-
analysis. BMJ 2001;323:101-5
Dr.P.Badrinath
Specialist Registrar in Public Health Medicine &
Honorary Clinical Lecturer, Suffolk Public Health Network &
University of Cambridge, Ipswich IP3 8LS.
Competing interests:
No competing interests
28 October 2002
Padmanabhabn Badrinath
Specialist Registrar in PHM & Honorary Clinical Lecturer
Suffolk Public Health Network & University of Cambridge, Ipswich IP3 8LS
Rapid Response:
Does the LANGUAGE bias deserve a mention?
Dear Editor,
The authors of the recent meta-analysis(1)on the management of
chronic illness need to be commended for their efforts. They have
generated evidence on the effectiveness of different disease management
programmes, which no doubt will be of interest to patients, and providers
of care. However, I was surprised to find that language bias has not been
addressed by the authors.
It has been shown(2) that authors are more likely to publish
randomised controlled trials (RCTs) in an English-language journal if the
results are significant. Hence, English language bias may be introduced in
reviews and meta-analyses if they include only trials reported in English.
There is mixed evidence on the impact of performing meta-analysis leaving
out papers published in languages other than English. Gregoire et al
(3)found that for 1 in 36 meta-analyses results and conclusions differed
when non-English papers were included in reanalysis. According to Juni et
al (4) excluding trials published in languages other than English
generally has little effect on summary treatment effect estimates but it
would be hard to predict the impact on individual systematic reviews.
I performed a quick search of Medline selecting all the non-English
languages and used the key words utilised by the authors in their search.
There were over 100 hits in the six different languages although it is not
known how many of these might be relevant. BMJ, which has published papers
on investigating (5)bias in meta-analysis, should have paid more attention
to the language bias in the discussion section of this publication.
References
1)Weingarten SR, Henning JM, Badamgarav E, Knight K, Hasselblad V, et
al. Interventions used in disease management programmes for patients with
chronic illness-which ones work? Meta-analysis of published reports. BMJ
2002;325:925.
2)Egger M, Zellweger-Zahner T, Schneider M, Junker C, Lengeler C,
Antes G. Language bias in randomised controlled trials published in
English and German. Lancet 1997;350(9074):326-9.
3)Gregoire G, Derderian F, Le Lorier J. Selecting the language of the
publications included in a meta-analysis: is there a Tower of Babel bias?
J Clin Epidemiol 1995;48(1):159-63.
4)Juni P, Holenstein F, Sterne J, Bartlett C, Egger M. Direction and
impact of language bias in meta-analyses of controlled trials: empirical
study. Int J Epidemiol 2002;31(1):115-23.
5)Sterne JA, Egger M, Smith GD. Systematic reviews in health care:
Investigating and dealing with publication and other biases in meta-
analysis. BMJ 2001;323:101-5
Dr.P.Badrinath
Specialist Registrar in Public Health Medicine &
Honorary Clinical Lecturer, Suffolk Public Health Network &
University of Cambridge, Ipswich IP3 8LS.
Competing interests: No competing interests