Strengthening the Reporting of Obrvational Studies in Epidemiology(STROBE):Explanation and Elaboration
Jan P.Vandenbroucke1,Erik von Elm2,3,Douglas G.Altman4,Peter C.Gøtzsche5,Cynthia D.Mulrow6,Stuart J.Pocock7, Charles Poole8,James J.Schleslman9,Matthias Egger2,10*for the STROBE Initiative
1Department of Clinical Epidemiology,Leiden University Medical Center,Leiden,The Netherlands,2Institute of Social&Preventive Medicine(ISPM),University of Bern,Bern, Switzerland,3Department of Medical Biometry and Medical Informatics,University Medical Centre,Freiburg,Germany,4Cancer Rearch UK/NHS Centre for Statistics in Medicine,Oxford,United Kingdom,5Nordic Cochrane Centre,Rigshospitalet,Copenhagen,Denmark,6University of Texas Health Science Center,San Antonio,United States of America,7Medical Statistics Unit,London School of Hygiene and Tropical Medicine,London,United Kingdom,8Department of Epidemiology,University of North Carolina School of Public Health,Chapel Hill,United States of America,9Department of Biostatistics,University of Pittsburgh Graduate School of Public Health,and University of Pittsburgh Cancer Institute,Pittsburgh,United States of America,10Department of Social Medicine,University of Bristol,Bristol,United Kingdom
Funding:The initial STROBE
workshop was funded by the
沧海一粟的意思European Science Foundation(ESF).
Additional funding was received from the Medical Rearch Council Health Services Rearch Collaboration and the National Health Services Rearch& Development Methodology Programme.The funders had no role in study design,data collection and analysis,decision to publish,or preparation of the manuscript. Competing Interests:The authors have declared that no competing interests exist.
Citation:Vandenbroucke JP,von Elm E,Altman DG,Gøtzsche PC,Mulrow CD,et al.(2007)Strengthening the Reporting of Obrvational Studies in Epidemiology(STROBE):Explanation and Elaboration.PLoS Med4(10):
e297.doi:10.1371/journal.pmed. 0040297
Received:July20,2007 Accepted:August30,2007 Published:October16,2007 Copyright:Ó2007Vandenbroucke et al.This is an open-access article distributed under the terms of th
e Creative Commons Attribution Licen,which permits unrestricted u,distribution,and reproduction in any medium,provided the original author and source are credited.In order to encourage dismination of the STROBE Statement,this article is freely available on the Web site of PLoS Medicine,and will also be published and made freely available by Epidemiology and Annals of Internal Medicine.The authors jointly hold the copyright of this article.For details on further u,e STROBE Web site(www.
strobe-statement/). Abbreviations:CI,confidence interval;RERI,Relative Excess Risk from Interaction;RR,relative risk; STROBE,Strengthening the Reporting of Obrvational Studies in Epidemiology
*To whom correspondence should be addresd.E-mail:strobe@ispm. unibe.ch
Much medical rearch is obrvational.The reporting of obrvational studies is often of insufficient quality.Poor reporting hampers the asssment of the strengths and weakness of a study and the generalisability of its results.Taking into account empirical evidence and theoretical considerations,a group of methodologists,rearchers,and editors developed the Strengthening the Reporting of Obrvational Studies in Epidemiology(STROBE)recommen-dations to improve the quality of reporti
方五洲
ng of obrvational studies.The STROBE Statement consists of a checklist of22items,which relate to the title,abstract,introduction,methods, results and discussion ctions of articles.Eighteen items are common to cohort studies,ca-control studies and cross-ctional 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 obrvational 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 u,understanding,and dismination of the STROBE Statement.The meaning and rationale for each checklist item are prented.For each item,one or veral published examples and,where possible,references to relevant empirical studies and methodological literature are provided.Examples of uful flow diagrams are also included. The STROBE Statement,this document,and the associated Web site(www. strobe-statement/)should be helpful resources to improve reporting of obrvational rearch.
P L o S MEDICINE
Introduction
Rational health care practices require knowledge about the aetiology and pathogenesis,diagnosis,pr
ognosis and treat-ment of dias.Randomid trials provide valuable evi-dence about treatments and other interventions.However, much of clinical or public health knowledge comes from obrvational rearch[1].About nine of ten rearch papers published in clinical speciality journals describe obrvatio-nal rearch[2,3].
The STROBE Statement
Reporting of obrvational rearch is often not detailed and clear enough to asss the strengths and weakness of the investigation[4,5].To improve the reporting of obr-vational rearch,we developed a checklist of items that should be addresd:the Strengthening the Reporting of Obrvational Studies in Epidemiology(STROBE)Statement (Table1).Items relate to title,abstract,introduction, methods,results and discussion ctions of articles.The STROBE Statement has recently been published in veral journals[6].Our aim is to ensure clear prentation of what was planned,done,and found in an obrvational study.We stress that the recommendations are not prescriptions for tting up or conducting studies,nor do they dictate methodology or mandate a uniform prentation. STROBE provides general reporting recommendations for descriptive obrvational studies and studies that investigate associations between exposures and health outcomes. STROBE address the three main types of obrvational studies:cohort,ca-con
trol and cross-ctional studies. Authors u diver terminology to describe the study designs.For instance,‘follow-up study’and‘longitudinal study’are ud as synonyms for‘cohort study’,and ‘prevalence study’as synonymous with‘cross-ctional study’. We cho the prent terminology becau it is in common u.Unfortunately,terminology is often ud incorrectly[7] or imprecily[8].In Box1we describe the hallmarks of the three study designs.
The Scope of Obrvational Rearch
Obrvational studies rve a wide range of purpos:from reporting afirst hint of a potential cau of a dia,to verifying the magnitude of previously reported associations. Ideas for studies may ari from clinical obrvations or from biologic insight.Ideas may also ari from informal looks at data that lead to further explorations.Like a clinician who has en thousands of patients,and notes one that strikes her attention,the rearcher may note something special in the data.Adjusting for multiple looks at the data may not be possible or desirable[9],but further studies to confirm or refute initial obrvations are often needed[10].Existing data may be ud to examine new ideas about potential causal factors,and may be sufficient for rejection or confirmation. In other instances,studies follow that are specifically designed to overcome potential problems with previous reports.The latter studies will gather new data and will be planned for that purpo,in contrast to analys of existing d
ata.This leads to diver ,on the merits of looking at subgroups or the importance of a predetermined sample size.STROBE tries to accommodate the diver us of obrvational rearch-from discovery to refutation or confirmation.Where necessary we will indicate in what circumstances specific recommendations apply.
How to U This Paper
This paper is linked to the shorter STROBE paper that introduced the items of the checklist in veral journals[6], and forms an integral part of the STROBE Statement.Our intention is to explain how to report rearch well,not how rearch should be done.We offer a detailed explanation for each checklist item.Each explanation is preceded by an example of what we consider transparent reporting.This does not mean that the study from which the example was taken was uniformly well reported or well done;nor does it mean that itsfindings were reliable,in the n that they were later confirmed by others:it only means that this particular item was well reported in that study.In addition to explanations and examples we included Boxes1–8with supplementary information.The are intended for readers who want to refresh their memories about some theoretical points,or be quickly informed about technical background details.A full understanding of the points may require studying the textbooks or methodological papers that are cited.
STROBE recommendations do not specifically address topics such as genetic linkage studies,infectious dia modelling or ca reports and ca ries[11,12].As many of the key elements in STROBE apply to the designs,authors who report such studies may neverthelessfind our recom-mendations uful.For authors of obrvational studies that specifically address diagnostic tests,tumour markers and genetic associations,STARD[13],REMARK[14],and STRE-GA[15]recommendations may be particularly uful.
The Items in the STROBE Checklist
We now discuss and explain the22items in the STROBE checklist(Table1),and give published examples for each item.Some examples have been edited by removing citations or spelling out abbreviations.Eighteen items apply to all three study designs whereas four are design-specific.Starred items(for example item8*)indicate that the information should be given parately for cas and controls in ca-control studies,or expod and unexpod groups in cohort and cross-ctional studies.We advi authors to address all items somewhere in their paper,but we do not prescribe a preci location or order.For instance,we discuss the reporting of results under a number of parate items,while recognizing that authors might address veral items within a single ction of text or in a table.
The Items
TITLE AND ABSTRACT
1(a).Indicate the study’s design with a commonly ud term in the title or the abstract.
Example
‘‘Leukaemia incidence among workers in the shoe and boot manufacturing industry:a ca-control study’’[18]. Explanation
Readers should be able to easily identify the design that was ud from the title or abstract.An explicit,commonly ud term for the study design also helps ensure correct indexing of articles in electronic databas[19,20].
Table1.The STROBE Statement—Checklist of Items That Should Be Addresd in Reports of Obrvational Studies
Item
number
Recommendation
TITLE and ABSTRACT1(a)Indicate the study’s design with a commonly ud term in the title or the abstract
(b)Provide in the abstract an informative and balanced summary of what was done and what was found
INTRODUCTION
Background/
rationale
2Explain the scientific background and rationale for the investigation being reported
Objectives3State specific objectives,including any prespecified hypothes
METHODS
Study design4Prent key elements of study design early in the paper
Setting5Describe the tting,locations,and relevant dates,including periods of recruitment,exposure,follow-up,and data collection Participants6(a)Cohort study—Give the eligibility criteria,and the sources and methods of lection of participants.Describe methods of
follow-up
Ca-control study—Give the eligibility criteria,and the sources and methods of ca ascertainment and control lection.Give
the rationale for the choice of cas and controls
Cross-ctional study—Give the eligibility criteria,and the sources and methods of lection of participants
(b)Cohort study—For matched studies,give matching criteria and number of expod and unexpod
Ca-control study—For matched studies,give matching criteria and the number of controls per ca
Variables7Clearly define all outcomes,exposures,predictors,potential confounders,and effect modifiers.Give diagnostic criteria,if applicable
Data sources/ measurement 8*For each variable of interest,give sources of data and details of methods of asssment(measurement).
Describe comparability of asssment methods if there is more than one group
Bias9Describe any efforts to address potential sources of bias
Study size10Explain how the study size was arrived at
Quantitative
variables
11Explain how quantitative variables were handled in the analys.If applicable,describe which groupings were chon,and why
Statistical methods 12(a)Describe all statistical methods,including tho ud to control for confounding
(b)Describe any methods ud to examine subgroups and interactions
(c)Explain how missing data were addresd
(d)Cohort study—If applicable,explain how loss to follow-up was addresd
Ca-control study—If applicable,explain how matching of cas and controls was addresd
Cross-ctional study—If applicable,describe analytical methods taking account of sampling strategy
(e)Describe any nsitivity analys
RESULTS
Participants13*(a)Report the numbers of individuals at each stage of the study—e.g.,numbers potentially eligible,examined for eligibility,confirmed eligible,included in the study,completing follow-up,and analyd
(b)Give reasons for non-participation at each stage
(c)Consider u of a flow diagram
Descriptive data 14*(a)Give characteristics of study ,demographic,clinical,social)and
information on exposures and potential confounders
(b)Indicate the number of participants with missing data for each variable of interest
(c)Cohort study—Summari follow-up ,average and total amount)
Outcome data15*Cohort study—Report numbers of outcome events or summary measures over time
Ca-control study—Report numbers in each exposure category,or summary measures of exposure
Cross-ctional study—Report numbers of outcome events or summary measures
Main results16(a)Give unadjusted estimates and,if applicable,confounder-adjusted estimates and their ,95%confidence interval).
Make clear which confounders were adjusted for and why they were included
(b)Report category boundaries when continuous variables were categorized
(c)If relevant,consider translating estimates of relative risk into absolute risk for a meaningful time pe
riod
Other
analys
17Report other analys done—e.g.,analys of subgroups and interactions,and nsitivity analys
DISCUSSION
Key results18Summari key results with reference to study objectives
Limitations19Discuss limitations of the study,taking into account sources of potential bias or imprecision.Discuss both direction and magnitude of any potential bias
Interpretation20Give a cautious overall interpretation of results considering objectives,limitations,multiplicity of analys,results from similar stu-dies,and other relevant evidence
Generalisability21Discuss the generalisability(external validity)of the study results
OTHER INFORMATION
现代诗冰心
Funding22Give the source of funding and the role of the funders for the prent study and,if applicable,for the original study on which the prent article is bad
自我介绍的英语怎么说*Give such information parately for cas and controls in ca-control studies,and,if applicable,for expod and unexpod groups in cohort and cross-ctional studies.
Note:An Explanation and Elaboration article discuss each checklist item and gives methodological background and published examples of transparent reporting.The STROBE checklist is best ud in conjunction with this article(freely available on the Web sites of PLoS Medicine at www.plosmedicine/,Annals of Internal Medicine at www.annals/,and Epidemiology at /).Separate versions of the checklist for cohort,ca-control,and cross-ctional studies are available on the STROBE Web site at www. strobe-statement/.
doi:10.1371/journal.pmed.0040297.t001
脸瘦
1(b).Provide in the abstract an informative and balanced summary of what was done and what was found. Example
‘‘Background:The expected survival of HIV-infected patients is of major public health interest.
狂人日记鲁迅Objective:To estimate survival time and age-specific mortal-ity rates of an HIV-infected population compared with that of the general population.
Design:Population-bad cohort study.
Setting:All HIV-infected persons receiving care in Denmark from1995to2005.Patients:Each member of the nationwide Danish HIV Cohort Study was matched with as many as99persons from the general population according to x,date of birth,and municipality of residence.
Measurements:The authors computed Kaplan–Meier life tables with age as the time scale to estimate survival from age 25years.Patients with HIV infection and corresponding persons from the general population were obrved from the date of the patient’s HIV diagnosis until death,emigration,or 1May2005.
Results:3990HIV-infected patients and379872persons from the general population were included in the study, yielding22744(median,5.8y/person)and2689287(median, 8.4years/person)person-years of obrvation.Three percent of participants were lost to follow-up.From age25years,the median survival was19.9years(95%CI,18.5to21.3)among patients with HIV infection and51.1years(CI,50.9to51.5) among the general population.For HIV-infected patients, survival increa
d to32.5years(CI,29.4to34.7)during the 2000to2005period.In the subgroup that excluded persons with known hepatitis C coinfection(16%),median survival was38.9years(CI,35.4to40.1)during this same period.The relative mortality rates for patients with HIV infection compared with tho for the general population decread with increasing age,whereas the excess mortality rate incread with increasing age.
Limitations:The obrved mortality rates are assumed to apply beyond the current maximum obrvation time of10 years.
Conclusions:The estimated median survival is more than35 years for a young person diagnod with HIV infection in the late highly active antiretroviral therapy era.However,an ongoing effort is still needed to further reduce mortality rates for the persons compared with the general population’’[21].
Explanation
The abstract provides key information that enables readers to understand a study and decide whether to read the article.Typical components include a statement of the rearch question,a short description of methods and results,and a conclusion[22].Abstracts should summarize key details of s
tudies and should only prent information that is provided in the article.We advi prenting key results in a numerical form that includes numbers of participants,estimates of associations and appropriate measures of variability and ,odds ratios with confidence intervals).We regard it insufficient to state only that an exposure is or is not significantly associated with an outcome.
A ries of headings pertaining to the background,design, conduct,and analysis of a study may help readers acquire the esntial information rapidly[23].Many journals require such structured abstracts,which tend to be of higher quality and more readily informative than unstructured summaries [24,25].
INTRODUCTION
The Introduction ction should describe why the study was done and what questions and hypothes it address.It should allow others to understand the study’s context and judge its potential contribution to current knowledge.
Box1.Main study designs covered by STROBE
Cohort,ca-control,and cross-ctional designs reprent different approaches of investigating the occurrence of health-related events in a given population and time period.The studies may address many types of health-related events,including dia or dia remission, disability or complications,death or survival,and the occurrence of risk factors.
In cohort studies,the investigators follow people over time.They obtain information about people and their exposures at baline,let time pass, and then asss the occurrence of outcomes.Investigators commonly make contrasts between individuals who are expod and not expod or among groups of individuals with different categories of exposure. Investigators may asss veral different outcomes,and examine exposure and outcome variables at multiple points during follow-up. Clod cohorts(for example birth cohorts)enrol a defined number of participants at study ont and follow them from that time forward, often at t intervals up to a fixed end date.In open cohorts the study population is dynamic:people enter and leave the population at different points in time(for example inhabitants of a town).Open cohorts change due to deaths,births,and migration,but the composition of the population with regard to variables such as age and gender may remain approximately constant,especially over a short period of time.In a clod cohort cumulative incidences(risks)and incidence rates can be estimated;when expod and unexpod groups are compared,this leads to risk ratio or rate ratio estimates.Open cohorts estimate incidence rates and rate ratios.
In ca-control studies,investigators compare exposures between people with a particular dia outcome(cas)and people without that outcome(controls).Investigators aim to collect cas and controls that are reprentative of an underlying cohort or a cross-ction of a population.That population can be defined geographically,but also more looly as the catchment area of health care facilities.The ca sample may be100%or a large fraction of available cas,while the control sample usually is only a small fraction of the people who do not have the pertinent outcome.Controls reprent the cohort or population of people from which the cas aro.Investigators calculate the ratio of the odds of exposures to putative caus of the dia among cas and controls(e Box7).Depending on the sampling strategy for cas and controls and the nature of the population studied,the odds ratio obtained in a ca-control study is interpreted as the risk ratio,rate ratio or(prevalence)odds ratio[16,17].The majority of published ca-control studies sample open cohorts and so allow direct estimations of rate ratios.
In cross-ctional studies,investigators asss all individuals in a sample at the same point in time,often to examine the prevalence of exposures, risk factors or dia.Some cross-ctional studies are analytical and aim to quantify potential causal associations between exposures and dia. Such studies may be analyd like a cohort study by comparing dia prevalence betwe
en exposure groups.They may also be analyd like a ca-control study by comparing the odds of exposure between groups with and without dia.A difficulty that can occur in any design but is particularly clear in cross-ctional studies is to establish that an exposure preceded the dia,although the time order of exposure and outcome may sometimes be clear.In a study in which the exposure variable is congenital or genetic,for example,we can be confident that the exposure preceded the dia,even if we are measuring both at the same time.
漂亮的房子图片2.Background/rationale:Explain the scientific background and rationale for the investigation being reported. Example
‘‘Concerns about the rising prevalence of obesity in children and adolescents have focud on the well docu-mented associations between childhood obesity and in-cread cardiovascular risk and mortality in adulthood. Childhood obesity has considerable social and psychological conquences within childhood and adolescence,yet little is known about social,socioeconomic,and psychological con-quences in adult life.A recent systematic review found no longitudinal studies on the outcomes of childhood obesity other than physical health outcomes and only two longitu-dinal studies of the socioeconomic effects of obesity in adolescence.Gortmaker et al.found that US women who had been obe in late adolescence in1981were less likely to be married and had lower
incomes ven years later than women who had not been overweight,while men who had been overweight were less likely to be married.Sargent et al.found that UK women,but not men,who had been obe at16years in1974earned7.4%less than their non-obe peers at age23. (...)We ud longitudinal data from the1970British birth cohort to examine the adult socioeconomic,educational, social,and psychological outcomes of childhood obesity’’[26]. Explanation
The scientific background of the study provides important context for readers.It ts the stage for the study and describes its focus.It gives an overview of what is known on a topic and what gaps in current knowledge are addresd by the study.Background material should note recent pertinent studies and any systematic reviews of pertinent studies.
3.Objectives:State specific objectives,including any prespecified hypothes.
Example
‘‘Our primary objectives were to1)determine the prevalence of domestic violence among female patients prenting to four community-bad,primary care,adult medicine practices that rve patients of diver socio-economic background and2)identify demographic and clinical differences between currently abud patients and patients not currently being abud’’[27].
Explanation
Objectives are the detailed aims of the study.Well crafted objectives specify populations,exposures and outcomes,and parameters that will be estimated.They may be formulated as specific hypothes or as questions that the study was designed to address.In some situations objectives may be less specific,for example,in early discovery phas.Regard-less,the report should clearly reflect the investigators’intentions.For example,if important subgroups or addi-tional analys were not the original aim of the study but aro during data analysis,they should be described accord-ingly(e also items4,17and20).
METHODS
The Methods ction should describe what was planned and what was done in sufficient detail to allow others to understand the esntial aspects of the study,to judge whether the methods were adequate to provide reliable and valid answers,and to asss whether any deviations from the original plan were reasonable.
4.Study design:Prent key elements of study design early in the paper.
Example
吓唬的近义词
‘‘We ud a ca-crossover design,a variation of a ca-control design that is appropriate when a brief exposure (driver’s phone u)caus a transient ri in the risk of a rare outcome(a crash).We compared a driver’s u of a mobile phone at the estimated time of a crash with the same driver’s u during another suitable time period.Becau drivers are their own controls,the design controls for characteristics of the driver that may affect the risk of a crash but do not change over a short period of time.As it is important that risks during control periods and crash trips are similar,we compared phone activity during the hazard interval(time immediately before the crash)with phone activity during control intervals(equivalent times during which participants were driving but did not crash)in the previous week’’[28]. Explanation
We advi prenting key elements of study design early in the methods ction(or at the end of the introduction)so that readers can understand the basics of the study.For example,authors should indicate that the study was a cohort study,which followed people over a particular time period, and describe the group of persons that comprid the cohort and their exposure status.Similarly,if the investigation ud a ca-control design,the cas and controls and their source population should be described.If the study was a cross-ctional survey,the population and the point in time at which the cross-ction was taken should be mentioned. When a study is a variant of the three main study
types,there is an additional need for clarity.For instance,for a ca-crossover study,one of the variants of the ca-control design, a succinct description of the principles was given in the example above[28].
We recommend that authors refrain from simply calling a study‘prospective’or‘retrospective’becau the terms are ill defined[29].One usage es cohort and prospective as synonymous and rerves the word retrospective for ca-control studies[30].A cond usage distinguishes prospective and retrospective cohort studies according to the timing of data collection relative to when the idea for the study was developed[31].A third usage distinguishes prospective and retrospective ca-control studies depending on whether the data about the exposure of interest existed when cas were lected[32].Some advi against using the terms[33],or adopting the alternatives‘concurrent’and‘historical’for describing cohort studies[34].In STROBE,we do not u the words prospective and retrospective,nor alternatives such as concurrent and historical.We recommend that,whenever authors u the words,they define what they mean.Most importantly,we recommend that authors describe exactly how and when data collection took place.
Thefirst part of the methods ction might also be the place to mention whether the report is one of veral from a study.If a new report is in line with the original aims of the study,this is usually indicate
d by referring to an earlier publication and by briefly restating the salient features of the study.However,the aims of a study may also evolve over time.
