Evidence map›Paper›PMID 22192231›Full record

ArticleTrials2011

Comparisons against baseline within randomised groups are often used and can be highly misleading.

J Martin Bland, Douglas G Altman

Abstract readComparative Study
PubMed Full text at PMC Publisher
In one paragraph

Article in Trials, 2011. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 95 papers, 12 of them syntheses that pooled it.

0numbers the graph read from it
0cells of the map it votes in
95citing papers in PubMed, 12 pooled it
–field-weighted citation impact
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

95 citing papers in PubMed, 12 syntheses or guidelines pooled it.

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  6. Measuring quality of life in trials including patients on haemodialysis: methodological issues surrounding the use of the Kidney Disease Quality of Life Questionnaire.Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association · 2022
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  20. Humour interventions for patients in palliative care-a randomized controlled trial.Supportive care in cancer : official journal of the Multinational Association of Supportive Care in Cancer · 2023
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35 more citing papers are in PubMed but not listed here.

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

2 authors.

J Martin BlandUniversity of York, Heslington, York, YO10 5DD, UK. martin.bland@york.ac.uk
Douglas G Altman

Funding

Cancer Research UK
6 · The paper itself

Abstract

backgroundIn randomised trials, rather than comparing randomised groups directly some researchers carry out a significance test comparing a baseline with a final measurement separately in each group.

methodsWe give several examples where this has been done. We use simulation to demonstrate that the procedure is invalid and also show this algebraically.

resultsThis approach is biased and invalid, producing conclusions which are, potentially, highly misleading. The actual alpha level of this procedure can be as high as 0.50 for two groups and 0.75 for three.

conclusionsRandomised groups should be compared directly by two-sample methods and separate tests against baseline are highly misleading.

Indexed as

AgingBack PainComputer SimulationFemaleHumansMenorrhagiaProbabilityRandomized Controlled Trials as Topic

Identifiers

PMID22192231
PMCPMC3286439

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.