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Observational Studies: Getting Clear about Transparency

August 2014
11(8):e1001711

DOI:10.1371/journal.pmed.1001711

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The PLOS Medicine Editors endorse four measures to ensure transparency in the analysis and reporting of observational studies. Please see later in the article for the Editors' Summary.

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Editorial

Observational Studies: Getting Clear about Transparency

The

PLOS Medicine

Editors

Extending the Standard

When publishing observational re-

search, what information should journals

make available to the medical community

before a result can be considered suffi-

ciently reliable to inform patient care or

health policy?

For clinical trials, editors and re-

searchers share the context of a reporting

standard (CONSORT and its modifica-

tions [1]), a requirement for prospective,

public registration of clinical trials [2],

and a number of laws (e.g., [3]) and

policies requiring data sharing. This

combination supports transparency in

the design, conduct, and reporting of

clinical trials, and has proven sufficiently

flexible to allow editors to define appro-

priate exceptions (e.g., [4]). Systematic

reviews and meta-analyses, which often

present a basis for clinical decisions, are

also subject to strict reporting guidelines

[5]. Public registration is available for

such studies, and PLOS Medicine has

long encouraged publication of the

review protocol alongside the study

report [6].

Should a similar framework apply to

observational studies? In a Guidance and

Guidelines article published recently in

PLOS Medicine, Peat and colleagues [7]

identify study registration, protocol publi-

cation, better study reporting, and data

sharing as key to improving the transpar-

ency of prognosis research, which encom-

passes both observational and interven-

tional studies. Case-control, cohort, and

cross-sectional studies, even when given

ethics review, are not subject to all of the

regulations that facilitate standardized

reporting of clinical trials. Nonetheless,

when observational studies provide the

best evidence available, they influence

clinical practice. Selective presentation of

analyses or non-publication of results can

therefore misinform patient care. As the

authors of the STROBE guidelines for

reporting observational studies have not-

ed, ‘‘Research should be reported trans-

parently so that readers can follow what

was planned, what was done, what was

found, and what conclusions were drawn’’

[8].

New Guidelines for

Observational Studies in

PLOS

Medicine

The PLOS Medicine editors, in recent

consultation with our editorial board,

endorse measures in four areas to advance

transparency in the analysis and reporting

of observational studies.

Quality of Study Reporting

PLOS Medicine already requires CON-

SORT checklists for the clinical trials that

we consider, and our current author

guidelines encourage authors to report

observational studies according to the

STROBE statement or its more special-

ized derivatives [8,9]. Additionally, we

endorse the following measure:

(1) Going forward PLOS Medi-

cine will require that the

STROBE checklist for co-

hort, case-control or cross-

sectional studies [10], and

the STARD checklist for

studies of diagnostic accu-

racy [11]are included with

manuscript submissions

and published alongside re-

ports of observational stud-

ies to which they apply.

Authors must complete the

appropriate reporting

checklist not only with page

references, but also with

sufficient text excerpted

from the manuscript to ex-

plain how they accom-

plished all applicable

items.

(Note: The EQUATOR Network

(www.equator-network.org) provides ac-

cess to reporting guidelines for additional

specific study types, and authors within the

particular research communities to which

they apply are encouraged to use these

guidelines when appropriate.)

Data Sharing

The PLOS data policy [12] lays out

requirements for data sharing in research

manuscripts submitted after March 1,

2014. Therefore,

(2) The PLOS Data Policy applies

to all research submitted to

PLOS Medicine, including ob-

servational studies.

Transparency Regarding What Was

Planned and What Was Done

Research reports should make clear the

distinction between hypothesis testing and

exploratory evaluation of research ques-

tions, each of which may have validity,

and both of which may occur in the same

manuscript. Consequently,

Citation: The PLOS Medicine Editors (2014) Observational Studies: Getting Clear about Transparency. PLoS

Med 11(8): e1001711. doi:10.1371/journal.pmed.1001711

Published August 26, 2014

the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in

any medium, provided the original author and source are credited.

Funding: The authors are each paid a salary by the Public Library of Science, and they wrote this editorial

during their salaried time.

Competing Interests: The authors’ individual competing interests are at http://www.plosmedicine.org/static/

editorsInterests.action. PLOS is funded partly through manuscript publication charges, but the PLOS Medic ine

Editors are paid a fixed salary (their salaries are not linked to the number of papers published in the

journal).

* E-mail: medicine_editors@plos.org

Provenance: Written by editorial staff; not externally peer reviewed

The PLOS Medicine Editors are Laureen Connell, Rhona MacDonald, Thomas McBride, Larry Peiperl, Amy Ross,

Paul Simpson, and Maggie Winker.

PLOS Medicine | www.plosmedicine.org 1 August 2014 | Volume 11 | Issue 8 | e1001711

(3) Going forward, PLOS Medi-

cine will require that reports

of observational studies

clearly specify the following

items:

(a) What specific hypotheses

the researchers intended

to test, and the analytical

methods by which they

planned to test them;

(b) What analyses they actual-

ly performed; and

differ from those that were

planned, authors must

provide transparent expla-

nations for differences

that affect the reliability

of the study’s results.

For example, if a reported analysis was

performed based on an interesting but

unanticipated pattern in the data, authors

must be clear that the analysis was data-

driven. If hypotheses that were not included

in the original study design later became

important to test because new evidence

became available from other studies, the

authors should explain the situation, so that

reviewers and readers need not wonder if

the additional analyses were driven post-

hoc by the authors’ own data.

Protocol Publication

PLOS Medicine already requires that

study protocols be submitted with reports

of clinical trials, and publishes these

alongside the accepted paper. According-

ly, for observational studies,

(4) Going forward, if a pros-

pective analysis plan (from

the study’s funding propos-

al, IRB or other ethics com-

mittee submission, study

protocol, or other planning

document written before

analyzing the data) was

used in designing an obser-

vational study, authors

must include the relevant

prospectively written docu-

ment with the manuscript

submission for access by

editors and reviewers and

eventual publication along-

side the accepted paper.

As with studies of any design, in some

cases the final analysis of an observational

study will necessarily differ from the

analysis plan (as a result of unforeseen

practical circumstances, changes requested

by peer reviewers, etc.). Under such

conditions, authors should explain why

analyses could not be completed as

planned, or why they had to be revised,

and thereby address potential concerns

over selective non-publication. If no pro-

spectively written document exists, authors

should explain how and when they

determined the analyses being reported.

Looking Forward: Registration?

Editors cannot anticipate, nor would we

desire to create rules for, every possible

situation. Ultimately readers must judge

the reliability of a study relative to their

own needs and criteria.

We believe that promoting transparency

by publishing prospective analysis plans

and accounting clearly for substantial

changes will help readers (including editors

and peer reviewers) to assess the reliability

of published observational research. Our

goal is not only to establish these practices

for PLOS Medicine but to advocate for

such transparency as a standard within the

research community.

We also recognize that no practice that

applies only to published reports can

guard against bias due to selective non-

publication of observational studies, an

issue that the open question of prospective

protocol registration could potentially

address [13–16]. ClinicalTrials.gov,

among other registries, already allows

registration of observational studies, and,

as technologies allowing the ‘‘flexibility to

update date-stamped protocols’’ [8] be-

come more widely available, it seems likely

that community standards for registration

will move toward the greater transparency

that such tools facilitate. At the same time,

new evidence published by Dwan and

colleagues in a recent issue of PLOS

Medicine indicate that, in the case of

clinical trials, substantial discrepancies

exist between registered and reported

analyses [17]. This result suggests that

prospective registration alone, should it

become the standard for observational

clinical research, will still be no sub-

stitute for a conscientious explanation of

differences between registered and actual

analyses.

Peat and colleagues have contributed to

this debate by calling for public registration

of prognostic research, arguing that

‘‘routine registration of all prognostic

studies, linked to an accessible study

protocol using agreed reporting guide-

lines, would improve transparency and

promote data sharing’’ [7]. They further

point out that protocol sharing and

registration are not equivalent: ‘‘Proto-

cols describe the rationale, objectives,

design, methodology, statistical consider-

ations, and organization of a study and

they present a research plan made before

the conduct of the study. Compared to

study registers, protocols contain more

detail, particularly about study design

and analysis plans.’’ Interestingly, while

registration of clinical trials is mandatory

under International Committee of Med-

ical Journal Editors (ICMJE) require-

ments, posting of trial protocols in

registries is optional [2].

The PLOS Medicine editors welcome

opportunities to collaborate with the

research community on issues of transpar-

ency and publication quality. We hope

authors will find our requirements con-

structive and will let us know of suggested

improvements. We encourage mem-

bers of the research community to

share your insights by commenting

on this editorial, either on the PLOS

Medicine site or in Pub Med Com-

mons, with thoughts on whether or

how medical journals should estab-

lish requirements for prospective,

public registration of observational

studies that are intended to inform

patient care or health policy. We

plan to revisit this issue in due course, and

your views will help us determine our

future direction.

Acknowledgments

The authors thank Dr. Virginia Barbour for her

comments on an earlier draft of this editorial,

and members of the PLOS Medicine Editorial

Board for thoughtful discussion of these issues.

Author Contributions

Wrote the first draft of the manuscript: LP.

Contributed to the writing of the manuscript:

LP LC RM AR PS MW TM. ICMJE criteria

for authorship read and met: LP LC RM AR

PS MW TM. Agree with manuscript results

and conclusions: LP LC RM AR PS MW

TM.

PLOS Medicine | www.plosmedicine.org 2 August 2014 | Volume 11 | Issue 8 | e1001711

References

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PLOS Medicine | www.plosmedicine.org 3 August 2014 | Volume 11 | Issue 8 | e1001711

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Much medical research is observational. The reporting of observational studies is often of insufficient quality. Poor reporting hampers the assessment of the strengths and weaknesses of a study and the generalisability of its results. Taking into account empirical evidence and theoretical considerations, a group of methodologists, researchers, and editors developed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) recommendations to improve the quality of reporting of observational studies. The STROBE Statement consists of a checklist of 22 items, which relate to the title, abstract, introduction, methods, results and discussion sections of articles. Eighteen items are common to cohort studies, case-control studies and cross-sectional studies and four are specific to each of the three study designs. The STROBE Statement provides guidance to authors about how to improve the reporting of observational studies and facilitates critical appraisal and interpretation of studies by reviewers, journal editors and readers. This explanatory and elaboration document is intended to enhance the use, understanding, and dissemination of the STROBE Statement. The meaning and rationale for each checklist item are presented. For each item, one or several published examples and, where possible, references to relevant empirical studies and methodological literature are provided. Examples of useful flow diagrams are also included. The STROBE Statement, this document, and the associated Web site (http://www.strobe-statement.org/) should be helpful resources to improve reporting of observational research.

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PLoS Medicine Editors

Improving the Transparency of Prognosis Research: The Role of Reporting, Data Sharing, Registration, and Protocols

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Full-text available

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PLOS MED

George Peat and colleagues review and discuss current approaches to transparency and published debates and concerns about efforts to standardize prognosis research practice, and make five recommendations. Please see later in the article for the Editors' Summary

Evidence for the Selective Reporting of Analyses and Discrepancies in Clinical Trials: A Systematic Review of Cohort Studies of Clinical Trials

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PLOS MED

Background: Most publications about selective reporting in clinical trials have focussed on outcomes. However, selective reporting of analyses for a given outcome may also affect the validity of findings. If analyses are selected on the basis of the results, reporting bias may occur. The aims of this study were to review and summarise the evidence from empirical cohort studies that assessed discrepant or selective reporting of analyses in randomised controlled trials (RCTs). Methods and findings: A systematic review was conducted and included cohort studies that assessed any aspect of the reporting of analyses of RCTs by comparing different trial documents, e.g., protocol compared to trial report, or different sections within a trial publication. The Cochrane Methodology Register, Medline (Ovid), PsycInfo (Ovid), and PubMed were searched on 5 February 2014. Two authors independently selected studies, performed data extraction, and assessed the methodological quality of the eligible studies. Twenty-two studies (containing 3,140 RCTs) published between 2000 and 2013 were included. Twenty-two studies reported on discrepancies between information given in different sources. Discrepancies were found in statistical analyses (eight studies), composite outcomes (one study), the handling of missing data (three studies), unadjusted versus adjusted analyses (three studies), handling of continuous data (three studies), and subgroup analyses (12 studies). Discrepancy rates varied, ranging from 7% (3/42) to 88% (7/8) in statistical analyses, 46% (36/79) to 82% (23/28) in adjusted versus unadjusted analyses, and 61% (11/18) to 100% (25/25) in subgroup analyses. This review is limited in that none of the included studies investigated the evidence for bias resulting from selective reporting of analyses. It was not possible to combine studies to provide overall summary estimates, and so the results of studies are discussed narratively. Conclusions: Discrepancies in analyses between publications and other study documentation were common, but reasons for these discrepancies were not discussed in the trial reports. To ensure transparency, protocols and statistical analysis plans need to be published, and investigators should adhere to these or explain discrepancies.

ORIGINAL ARTICLES The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies

Article

Full-text available

Jan 2009
UroToday

Much of biomedical research is observational. The reporting of such research is often inadequate, which hampers the assessment of its strengths and weaknesses and of a study's generalizability. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) Initiative developed recommendations on what should be included in an accurate and complete report of an observational study. We defined the scope of the recommendations to cover three main study designs: cohort, caseecontrol, and cross-sectional studies. We convened a 2-day workshop in September 2004, with methodologists, researchers, and journal editors to draft a checklist of items. This list was subsequently revised during several meetings of the coordinating group and in e-mail discussions with the larger group of STROBE contributors, taking into account empirical evidence and methodological considerations. The workshop and the subsequent iterative process of consultation and revision resulted in a checklist of 22 items (the STROBE Statement) that relate to the title, abstract, introduction, methods, results, and discussion sections of articles. Eighteen items are common to all three study designs and four are specific for cohort, caseecontrol, or cross-sectional studies. A detailed Explanation and Elaboration document is published separately and is freely available on the web sites of PLoS Medicine, Annals of Internal Medicine, and Epidemiology. We hope that the STROBE Statement will contribute to improving the quality of reporting of observational studies. 2007 The authors. Published by Elsevier Inc. All rights reserved.

Strengthening the Reporting of Observational Studies in Epidemiology (STROBE): Explanation and Elaboration

Article

Full-text available

Oct 2007
PLOS MED

CONSORT 2010 Statement: updated guidelines for reporting parallel group randomised trials

Article

Sep 2010

The CONSORT statement is used worldwide to improve the reporting of randomised controlled trials. Kenneth Schulz and colleagues describe the latest version, CONSORT 2010, which updates the reporting guideline based on new methodological evidence and accumulating experience. To encourage dissemination of the CONSORT 2010 Statement, this article is freely accessible on www.ijph.it.

The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) Statement: Guidelines for Reporting Observational Studies

Article

Oct 2007

Erik von Elm

Much biomedical research is observational. The reporting of such research is often inadequate, which hampers the assessment of its strengths and weaknesses and of a study's generalizability. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) Initiative developed recommendations on what should be included in an accurate and complete report of an observational study. We defined the scope of the recommendations to cover 3 main study designs: cohort, case-control, and cross-sectional studies. We convened a 2-day workshop in September 2004, with methodologists, researchers, and journal editors, to draft a checklist of items. This list was subsequently revised during several meetings of the coordinating group and in e-mail discussions with the larger group of STROBE contributors, taking into account empirical evidence and methodological considerations. The workshop and the subsequent iterative process of consultation and revision resulted in a checklist of 22 items (the STROBE Statement) that relate to the title, abstract, introduction, methods, results, and discussion sections of articles. Eighteen items are common to all 3 study designs and 4 are specific for cohort, case-control, or cross-sectional studies. A detailed Explanation and Elaboration document is published separately and is freely available at www.annals.org and on the Web sites of PLoS Medicine and Epidemiology. We hope that the STROBE Statement will contribute to improving the quality of reporting of observational studies.

Registration of observational studies: Is it time?

Article

Oct 2010
CAN MED ASSOC J

Observational studies form an important part of the medical evidence base, particularly for assessing rare adverse events and long-term effectiveness of medications and devices.1 However, observational studies, like interventional studies (clinical trials), are subject to publication bias and reporting bias.2–4 Registration of clinical trials is a widely recognized tool for facilitating complete public reporting.5 Registration of observational studies has received less attention, although interest is growing.6–8 Because existing registries (e.g., ClinicalTrials.gov) accommodate observational studies, and the rationale and benefits of registration are similar, we ask the scientific community and other stakeholders to consider the systematic, prospective registration of observational studies.

Observational Studies: Getting Clear about Transparency

Abstract

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