Observer bias in randomized clinical trials with measurement scale outcomes: a systematic review of trials with both blinded and nonblinded assessors
Identifieur interne : 000438 ( Pmc/Curation ); précédent : 000437; suivant : 000439Observer bias in randomized clinical trials with measurement scale outcomes: a systematic review of trials with both blinded and nonblinded assessors
Auteurs : Asbj Rn Hr Bjartsson ; Ann Sofia Skou Thomsen ; Frida Emanuelsson ; Britta Tendal ; J Rgen Hilden ; Isabelle Boutron ; Philippe Ravaud ; Stig BrorsonSource :
- CMAJ : Canadian Medical Association Journal [ 0820-3946 ] ; 2013.
Abstract
Clinical trials are commonly done without blinded outcome assessors despite the risk of bias. We wanted to evaluate the effect of nonblinded outcome assessment on estimated effects in randomized clinical trials with outcomes that involved subjective measurement scales.
We conducted a systematic review of randomized clinical trials with both blinded and nonblinded assessment of the same measurement scale outcome. We searched PubMed, EMBASE, PsycINFO, CINAHL, Cochrane Central Register of Controlled Trials, HighWire Press and Google Scholar for relevant studies. Two investigators agreed on the inclusion of trials and the outcome scale. For each trial, we calculated the difference in effect size (i.e., standardized mean difference between nonblinded and blinded assessments). A difference in effect size of less than 0 suggested that nonblinded assessors generated more optimistic estimates of effect. We pooled the differences in effect size using inverse variance random-effects meta-analysis and used metaregression to identify potential reasons for variation.
We included 24 trials in our review. The main meta-analysis included 16 trials (involving 2854 patients) with subjective outcomes. The estimated treatment effect was more beneficial when based on nonblinded assessors (pooled difference in effect size −0.23 [95% confidence interval (CI) −0.40 to −0.06]). In relative terms, nonblinded assessors exaggerated the pooled effect size by 68% (95% CI 14% to 230%). Heterogeneity was moderate (
We provide empirical evidence for observer bias in randomized clinical trials with subjective measurement scale outcomes. A failure to blind assessors of outcomes in such trials results in a high risk of substantial bias.
Url:
DOI: 10.1503/cmaj.120744
PubMed: 23359047
PubMed Central: 3589328
Links toward previous steps (curation, corpus...)
- to stream Pmc, to step Corpus: Pour aller vers cette notice dans l'étape Curation :000441
Links to Exploration step
PMC:3589328Le document en format XML
<record><TEI><teiHeader><fileDesc><titleStmt><title xml:lang="en">Observer bias in randomized clinical trials with measurement scale outcomes: a systematic review of trials with both blinded and nonblinded assessors</title>
<author><name sortKey="Hr Bjartsson, Asbj Rn" sort="Hr Bjartsson, Asbj Rn" uniqKey="Hr Bjartsson A" first="Asbj Rn" last="Hr Bjartsson">Asbj Rn Hr Bjartsson</name>
</author>
<author><name sortKey="Thomsen, Ann Sofia Skou" sort="Thomsen, Ann Sofia Skou" uniqKey="Thomsen A" first="Ann Sofia Skou" last="Thomsen">Ann Sofia Skou Thomsen</name>
</author>
<author><name sortKey="Emanuelsson, Frida" sort="Emanuelsson, Frida" uniqKey="Emanuelsson F" first="Frida" last="Emanuelsson">Frida Emanuelsson</name>
</author>
<author><name sortKey="Tendal, Britta" sort="Tendal, Britta" uniqKey="Tendal B" first="Britta" last="Tendal">Britta Tendal</name>
</author>
<author><name sortKey="Hilden, J Rgen" sort="Hilden, J Rgen" uniqKey="Hilden J" first="J Rgen" last="Hilden">J Rgen Hilden</name>
</author>
<author><name sortKey="Boutron, Isabelle" sort="Boutron, Isabelle" uniqKey="Boutron I" first="Isabelle" last="Boutron">Isabelle Boutron</name>
</author>
<author><name sortKey="Ravaud, Philippe" sort="Ravaud, Philippe" uniqKey="Ravaud P" first="Philippe" last="Ravaud">Philippe Ravaud</name>
</author>
<author><name sortKey="Brorson, Stig" sort="Brorson, Stig" uniqKey="Brorson S" first="Stig" last="Brorson">Stig Brorson</name>
</author>
</titleStmt>
<publicationStmt><idno type="wicri:source">PMC</idno>
<idno type="pmid">23359047</idno>
<idno type="pmc">3589328</idno>
<idno type="url">http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3589328</idno>
<idno type="RBID">PMC:3589328</idno>
<idno type="doi">10.1503/cmaj.120744</idno>
<date when="2013">2013</date>
<idno type="wicri:Area/Pmc/Corpus">000441</idno>
<idno type="wicri:explorRef" wicri:stream="Pmc" wicri:step="Corpus" wicri:corpus="PMC">000441</idno>
<idno type="wicri:Area/Pmc/Curation">000438</idno>
<idno type="wicri:explorRef" wicri:stream="Pmc" wicri:step="Curation">000438</idno>
</publicationStmt>
<sourceDesc><biblStruct><analytic><title xml:lang="en" level="a" type="main">Observer bias in randomized clinical trials with measurement scale outcomes: a systematic review of trials with both blinded and nonblinded assessors</title>
<author><name sortKey="Hr Bjartsson, Asbj Rn" sort="Hr Bjartsson, Asbj Rn" uniqKey="Hr Bjartsson A" first="Asbj Rn" last="Hr Bjartsson">Asbj Rn Hr Bjartsson</name>
</author>
<author><name sortKey="Thomsen, Ann Sofia Skou" sort="Thomsen, Ann Sofia Skou" uniqKey="Thomsen A" first="Ann Sofia Skou" last="Thomsen">Ann Sofia Skou Thomsen</name>
</author>
<author><name sortKey="Emanuelsson, Frida" sort="Emanuelsson, Frida" uniqKey="Emanuelsson F" first="Frida" last="Emanuelsson">Frida Emanuelsson</name>
</author>
<author><name sortKey="Tendal, Britta" sort="Tendal, Britta" uniqKey="Tendal B" first="Britta" last="Tendal">Britta Tendal</name>
</author>
<author><name sortKey="Hilden, J Rgen" sort="Hilden, J Rgen" uniqKey="Hilden J" first="J Rgen" last="Hilden">J Rgen Hilden</name>
</author>
<author><name sortKey="Boutron, Isabelle" sort="Boutron, Isabelle" uniqKey="Boutron I" first="Isabelle" last="Boutron">Isabelle Boutron</name>
</author>
<author><name sortKey="Ravaud, Philippe" sort="Ravaud, Philippe" uniqKey="Ravaud P" first="Philippe" last="Ravaud">Philippe Ravaud</name>
</author>
<author><name sortKey="Brorson, Stig" sort="Brorson, Stig" uniqKey="Brorson S" first="Stig" last="Brorson">Stig Brorson</name>
</author>
</analytic>
<series><title level="j">CMAJ : Canadian Medical Association Journal</title>
<idno type="ISSN">0820-3946</idno>
<idno type="eISSN">1488-2329</idno>
<imprint><date when="2013">2013</date>
</imprint>
</series>
</biblStruct>
</sourceDesc>
</fileDesc>
<profileDesc><textClass></textClass>
</profileDesc>
</teiHeader>
<front><div type="abstract" xml:lang="en"><sec><title>Background:</title>
<p>Clinical trials are commonly done without blinded outcome assessors despite the risk of bias. We wanted to evaluate the effect of nonblinded outcome assessment on estimated effects in randomized clinical trials with outcomes that involved subjective measurement scales.</p>
</sec>
<sec><title>Methods:</title>
<p>We conducted a systematic review of randomized clinical trials with both blinded and nonblinded assessment of the same measurement scale outcome. We searched PubMed, EMBASE, PsycINFO, CINAHL, Cochrane Central Register of Controlled Trials, HighWire Press and Google Scholar for relevant studies. Two investigators agreed on the inclusion of trials and the outcome scale. For each trial, we calculated the difference in effect size (i.e., standardized mean difference between nonblinded and blinded assessments). A difference in effect size of less than 0 suggested that nonblinded assessors generated more optimistic estimates of effect. We pooled the differences in effect size using inverse variance random-effects meta-analysis and used metaregression to identify potential reasons for variation.</p>
</sec>
<sec><title>Results:</title>
<p>We included 24 trials in our review. The main meta-analysis included 16 trials (involving 2854 patients) with subjective outcomes. The estimated treatment effect was more beneficial when based on nonblinded assessors (pooled difference in effect size −0.23 [95% confidence interval (CI) −0.40 to −0.06]). In relative terms, nonblinded assessors exaggerated the pooled effect size by 68% (95% CI 14% to 230%). Heterogeneity was moderate (<italic>I</italic>
<italic><sup>2</sup>
</italic>
= 46%, <italic>p</italic>
= 0.02) and unexplained by metaregression.</p>
</sec>
<sec><title>Interpretation:</title>
<p>We provide empirical evidence for observer bias in randomized clinical trials with subjective measurement scale outcomes. A failure to blind assessors of outcomes in such trials results in a high risk of substantial bias.</p>
</sec>
</div>
</front>
</TEI>
<pmc article-type="research-article"><pmc-comment>The publisher of this article does not allow downloading of the full text in XML form.</pmc-comment>
<front><journal-meta><journal-id journal-id-type="nlm-ta">CMAJ</journal-id>
<journal-id journal-id-type="iso-abbrev">CMAJ</journal-id>
<journal-id journal-id-type="publisher-id">9711805</journal-id>
<journal-title-group><journal-title>CMAJ : Canadian Medical Association Journal</journal-title>
</journal-title-group>
<issn pub-type="ppub">0820-3946</issn>
<issn pub-type="epub">1488-2329</issn>
<publisher><publisher-name>Canadian Medical Association</publisher-name>
</publisher>
</journal-meta>
<article-meta><article-id pub-id-type="pmid">23359047</article-id>
<article-id pub-id-type="pmc">3589328</article-id>
<article-id pub-id-type="doi">10.1503/cmaj.120744</article-id>
<article-id pub-id-type="publisher-id">185e201</article-id>
<article-categories><subj-group subj-group-type="heading"><subject>Research</subject>
</subj-group>
</article-categories>
<title-group><article-title>Observer bias in randomized clinical trials with measurement scale outcomes: a systematic review of trials with both blinded and nonblinded assessors</article-title>
</title-group>
<contrib-group><contrib contrib-type="author"><name><surname>Hróbjartsson</surname>
<given-names>Asbjørn</given-names>
</name>
<degrees>MD PhD</degrees>
<xref ref-type="corresp" rid="c1-185e201"></xref>
</contrib>
<contrib contrib-type="author"><name><surname>Thomsen</surname>
<given-names>Ann Sofia Skou</given-names>
</name>
<degrees>MD</degrees>
</contrib>
<contrib contrib-type="author"><name><surname>Emanuelsson</surname>
<given-names>Frida</given-names>
</name>
<degrees>MD</degrees>
</contrib>
<contrib contrib-type="author"><name><surname>Tendal</surname>
<given-names>Britta</given-names>
</name>
<degrees>MD PhD</degrees>
</contrib>
<contrib contrib-type="author"><name><surname>Hilden</surname>
<given-names>Jørgen</given-names>
</name>
<degrees>MD</degrees>
</contrib>
<contrib contrib-type="author"><name><surname>Boutron</surname>
<given-names>Isabelle</given-names>
</name>
<degrees>MD PhD</degrees>
</contrib>
<contrib contrib-type="author"><name><surname>Ravaud</surname>
<given-names>Philippe</given-names>
</name>
<degrees>MD PhD</degrees>
</contrib>
<contrib contrib-type="author"><name><surname>Brorson</surname>
<given-names>Stig</given-names>
</name>
<degrees>MD PhD</degrees>
</contrib>
<aff id="af1-185e201">From the Nordic Cochrane Centre (Hróbjartsson, Thomsen, Emanuelsson, Tendal) Rigshospitalet Department 7811, Copenhagen, Denmark; the Department of Biostatistics (Hilden), University of Copenhagen, Denmark; the French Cochrane Centre (Boutron, Ravaud), Assistance Publique (Hotel Dieu), Paris, France; and the Department of Orthopaedic Surgery (Brorson), Herlev University Hospital, Denmark.</aff>
</contrib-group>
<author-notes><corresp id="c1-185e201"><bold>Correspondence to:</bold>
Asbjørn Hróbjartsson, <email>ah@cochrane.dk</email>
</corresp>
</author-notes>
<pub-date pub-type="ppub"><day>5</day>
<month>3</month>
<year>2013</year>
</pub-date>
<volume>185</volume>
<issue>4</issue>
<fpage>E201</fpage>
<lpage>E211</lpage>
<permissions><copyright-statement>© 1995-2013, Canadian Medical Association</copyright-statement>
<copyright-year>2013</copyright-year>
</permissions>
<abstract><sec><title>Background:</title>
<p>Clinical trials are commonly done without blinded outcome assessors despite the risk of bias. We wanted to evaluate the effect of nonblinded outcome assessment on estimated effects in randomized clinical trials with outcomes that involved subjective measurement scales.</p>
</sec>
<sec><title>Methods:</title>
<p>We conducted a systematic review of randomized clinical trials with both blinded and nonblinded assessment of the same measurement scale outcome. We searched PubMed, EMBASE, PsycINFO, CINAHL, Cochrane Central Register of Controlled Trials, HighWire Press and Google Scholar for relevant studies. Two investigators agreed on the inclusion of trials and the outcome scale. For each trial, we calculated the difference in effect size (i.e., standardized mean difference between nonblinded and blinded assessments). A difference in effect size of less than 0 suggested that nonblinded assessors generated more optimistic estimates of effect. We pooled the differences in effect size using inverse variance random-effects meta-analysis and used metaregression to identify potential reasons for variation.</p>
</sec>
<sec><title>Results:</title>
<p>We included 24 trials in our review. The main meta-analysis included 16 trials (involving 2854 patients) with subjective outcomes. The estimated treatment effect was more beneficial when based on nonblinded assessors (pooled difference in effect size −0.23 [95% confidence interval (CI) −0.40 to −0.06]). In relative terms, nonblinded assessors exaggerated the pooled effect size by 68% (95% CI 14% to 230%). Heterogeneity was moderate (<italic>I</italic>
<italic><sup>2</sup>
</italic>
= 46%, <italic>p</italic>
= 0.02) and unexplained by metaregression.</p>
</sec>
<sec><title>Interpretation:</title>
<p>We provide empirical evidence for observer bias in randomized clinical trials with subjective measurement scale outcomes. A failure to blind assessors of outcomes in such trials results in a high risk of substantial bias.</p>
</sec>
</abstract>
</article-meta>
</front>
</pmc>
</record>
Pour manipuler ce document sous Unix (Dilib)
EXPLOR_STEP=$WICRI_ROOT/Wicri/Sante/explor/ParkinsonFranceV1/Data/Pmc/Curation
HfdSelect -h $EXPLOR_STEP/biblio.hfd -nk 000438 | SxmlIndent | more
Ou
HfdSelect -h $EXPLOR_AREA/Data/Pmc/Curation/biblio.hfd -nk 000438 | SxmlIndent | more
Pour mettre un lien sur cette page dans le réseau Wicri
{{Explor lien |wiki= Wicri/Sante |area= ParkinsonFranceV1 |flux= Pmc |étape= Curation |type= RBID |clé= PMC:3589328 |texte= Observer bias in randomized clinical trials with measurement scale outcomes: a systematic review of trials with both blinded and nonblinded assessors }}
Pour générer des pages wiki
HfdIndexSelect -h $EXPLOR_AREA/Data/Pmc/Curation/RBID.i -Sk "pubmed:23359047" \ | HfdSelect -Kh $EXPLOR_AREA/Data/Pmc/Curation/biblio.hfd \ | NlmPubMed2Wicri -a ParkinsonFranceV1
![]() | This area was generated with Dilib version V0.6.29. | ![]() |