Outcome reporting bias in randomised trials
<p>Background</p> <p>Selective reporting of outcomes within a published study based on their nature or direction can result in systematic differences between reported and unreported data. Direct evidence of outcome reporting bias is limited to case reports.</p> <p>Obje...
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| Format: | Thèse |
| Langue: | English |
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2003
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| _version_ | 1826281889839710208 |
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| author | Chan, A Chan, An-Wen |
| author2 | Altman, D |
| author_facet | Altman, D Chan, A Chan, An-Wen |
| author_sort | Chan, A |
| collection | OXFORD |
| description | <p>Background</p> <p>Selective reporting of outcomes within a published study based on their nature or direction can result in systematic differences between reported and unreported data. Direct evidence of outcome reporting bias is limited to case reports.</p> <p>Objective</p> <p>To study empirically the nature of outcome reporting bias in randomised controlled trials (RCTs).</p> <p>Methods</p> <p>Three cohorts of RCTs were identified: PubMed-indexed RCTs published in December 2000; trial protocols approved by a Danish ethics committee from 1994-95; and trial protocols funded by a government agency in Canada from 1990-98. Data on reported and unreported outcomes were recorded from all trial publications and a survey of authors. An outcome was considered incompletely reported if insufficient data were presented for meta-analysis. Odds ratios relating the completeness of outcome reporting to statistical significance were calculated for each trial, and then pooled using a random effects meta-analysis. Protocols and publications were also reviewed for discrepancies in primary outcome reporting.</p> <p>Results</p> <p>519 trials with 10,557 outcomes, 102 trials with 3613 outcomes, and 48 trials with 1390 outcomes were identified for the PubMed, ethics committee, and funding agency cohorts respectively. 22%-35% of outcomes per parallel group study were, on average, incompletely reported for meta-analysis. Fully reported outcomes had a two- to three-fold higher odds of being statistically significant compared to incompletely reported outcomes. The most common reasons given for omitting outcomes included a lack of clinical importance, lack of statistical significance, and space constraints. Major discrepancies between primary outcomes in protocols and publications were found in one half of trials.</p> <p>Discussion and conclusions</p> <p>The reporting of trial outcomes is frequently inadequate for meta-analysis; is biased to favour statistical significance; and is inconsistent with pre-specified protocol outcomes. Unacknowledged modifications to outcomes specified in trial protocols constitute scientific misconduct. Meta-analyses may therefore produce inflated and unreliable estimates of treatment effect.</p> |
| first_indexed | 2024-03-07T00:35:36Z |
| format | Thesis |
| id | oxford-uuid:8149b902-cb7f-487b-b187-67604eb87463 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T00:35:36Z |
| publishDate | 2003 |
| record_format | dspace |
| spelling | oxford-uuid:8149b902-cb7f-487b-b187-67604eb874632022-03-26T21:29:23ZOutcome reporting bias in randomised trialsThesishttp://purl.org/coar/resource_type/c_db06uuid:8149b902-cb7f-487b-b187-67604eb87463Systematic reviews (Medical research)Evidence-based medicineResearchMedicineEvaluationClinical trialsEnglishPolonsky Theses Digitisation Project2003Chan, AChan, An-WenAltman, DAltman, D<p>Background</p> <p>Selective reporting of outcomes within a published study based on their nature or direction can result in systematic differences between reported and unreported data. Direct evidence of outcome reporting bias is limited to case reports.</p> <p>Objective</p> <p>To study empirically the nature of outcome reporting bias in randomised controlled trials (RCTs).</p> <p>Methods</p> <p>Three cohorts of RCTs were identified: PubMed-indexed RCTs published in December 2000; trial protocols approved by a Danish ethics committee from 1994-95; and trial protocols funded by a government agency in Canada from 1990-98. Data on reported and unreported outcomes were recorded from all trial publications and a survey of authors. An outcome was considered incompletely reported if insufficient data were presented for meta-analysis. Odds ratios relating the completeness of outcome reporting to statistical significance were calculated for each trial, and then pooled using a random effects meta-analysis. Protocols and publications were also reviewed for discrepancies in primary outcome reporting.</p> <p>Results</p> <p>519 trials with 10,557 outcomes, 102 trials with 3613 outcomes, and 48 trials with 1390 outcomes were identified for the PubMed, ethics committee, and funding agency cohorts respectively. 22%-35% of outcomes per parallel group study were, on average, incompletely reported for meta-analysis. Fully reported outcomes had a two- to three-fold higher odds of being statistically significant compared to incompletely reported outcomes. The most common reasons given for omitting outcomes included a lack of clinical importance, lack of statistical significance, and space constraints. Major discrepancies between primary outcomes in protocols and publications were found in one half of trials.</p> <p>Discussion and conclusions</p> <p>The reporting of trial outcomes is frequently inadequate for meta-analysis; is biased to favour statistical significance; and is inconsistent with pre-specified protocol outcomes. Unacknowledged modifications to outcomes specified in trial protocols constitute scientific misconduct. Meta-analyses may therefore produce inflated and unreliable estimates of treatment effect.</p> |
| spellingShingle | Systematic reviews (Medical research) Evidence-based medicine Research Medicine Evaluation Clinical trials Chan, A Chan, An-Wen Outcome reporting bias in randomised trials |
| title | Outcome reporting bias in randomised trials |
| title_full | Outcome reporting bias in randomised trials |
| title_fullStr | Outcome reporting bias in randomised trials |
| title_full_unstemmed | Outcome reporting bias in randomised trials |
| title_short | Outcome reporting bias in randomised trials |
| title_sort | outcome reporting bias in randomised trials |
| topic | Systematic reviews (Medical research) Evidence-based medicine Research Medicine Evaluation Clinical trials |
| work_keys_str_mv | AT chana outcomereportingbiasinrandomisedtrials AT chananwen outcomereportingbiasinrandomisedtrials |