Evidence map›Paper›PMID 31315665›Full record

ArticleSystematic reviews2019

The strong focus on positive results in abstracts may cause bias in systematic reviews: a case study on abstract reporting bias.

Bram Duyx, Gerard M H Swaen, Miriam J E Urlings, Lex M Bouter, Maurice P Zeegers

Open access · goldAbstract read
PubMed Full text at PMC Publisher
In one paragraph

Article in Systematic reviews, 2019. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 20 papers, 11 of them syntheses that pooled it.

0numbers the graph read from it
0cells of the map it votes in
20citing papers in PubMed, 11 pooled it
2.8field-weighted citation impact, top 7% of its field
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

20 citing papers in PubMed, 11 syntheses or guidelines pooled it, 47 citations in OpenAlex.

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  8. Systematic review and meta-analysis efficacy and safety of immune checkpoint inhibitors in advanced melanoma patients with anti-PD-1 progression: a systematic review and meta-analysis.Clinical & translational oncology : official publication of the Federation of Spanish Oncology Societies and of the National Cancer Institute of Mexico · 2021
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4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

5 authors at 2 institutions in 1 country.

Bram DuyxNutrition and Translational Research in Metabolism (School NUTRIM), Maastricht University, Maastricht, The Netherlands. b.duyx@maastrichtuniversity.nl.
Gerard M H SwaenNutrition and Translational Research in Metabolism (School NUTRIM), Maastricht University, Maastricht, The Netherlands.
Miriam J E UrlingsNutrition and Translational Research in Metabolism (School NUTRIM), Maastricht University, Maastricht, The Netherlands.
Lex M BouterDepartment of Epidemiology and Biostatistics, Amsterdam University Medical Centers, Amsterdam, The Netherlands.
Maurice P ZeegersNutrition and Translational Research in Metabolism (School NUTRIM), Maastricht University, Maastricht, The Netherlands.
Maastricht University · NLAmsterdam University Medical Centers · NL

Funding

No grant is acknowledged in the PubMed record.

6 · The paper itself

Abstract

backgroundResearch articles tend to focus on positive findings in their abstract, especially if multiple outcomes have been studied. At the same time, search queries in databases are generally limited to the abstract, title and keywords fields of an article. Negative findings are therefore less likely to be detected by systematic searches and to appear in systematic reviews. We aim to assess the occurrence of this 'abstract reporting bias' and quantify its impact in the literature on the association between diesel exhaust exposure (DEE) and bladder cancer.

methodsWe set up a broad search query related to DEE and cancer in general. Full-texts of the articles identified in the search output were manually scanned. Articles were included if they reported, anywhere in the full-text, the association between DEE and bladder cancer. We assume that the use of a broad search query and manual full-text scanning allowed us to catch all the relevant articles, including those in which bladder cancer was not mentioned in the abstract, title or keywords.

resultsWe identified 28 articles. Only 12 of these (43%) had mentioned bladder in their abstract, title or keywords. A meta-analysis based on these 12 detectable articles yielded a pooled risk estimate of 1.10 (95% confidence interval [CI] 0.97-1.25), whereas the meta-analysis based on all 28 articles yielded a pooled estimate of 1.03 (95% CI 0.96-1.11).

conclusionsThis case study on abstract reporting bias shows that (a) more than half of all relevant articles were missed by a conventional search query and (b) this led to an overestimation of the pooled effect. Detection of articles will be improved if all studied exposure and outcome variables are reported in the keywords. The restriction on the maximum number of keywords should be lifted.

Indexed as

Abstracting and IndexingBiomedical ResearchNeoplasmsBiasHumansSystematic Reviews as TopicAbstractBladder cancerDiesel exhaust exposureEpidemiologyKeywordsReporting biasSearch enginesSystematic reviews

Identifiers

PMID31315665
PMCPMC6637611
OpenAlexW2956934712

What OpenQuestion holds

Textmetadata
LicenceCC BY
Read underepoch 390

Registered trials

None linked

Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.