1 how to write a study protocol epiet, lazareto, menorca september 2011 viviane bremer
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How to write a study protocol
EPIET, Lazareto, MenorcaSeptember 2011
Viviane Bremer
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What is the study protocol?
• Every step of a study
• Answers relevant questions- public health problem important?- study question relevant to problem?- objectives consistent with study question?- study design achieves objectives?- sufficient power?- public health impact of the findings?
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Why write a study protocol?
• Check - if objectives can be achieved- feasibility of the study
• Prevent failure to collect crucial information• Lays down the rules for all partners (quality)• Obtain approval of ethical committee(s)• Application for funds
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Study protocolHow to start ?
• Formulate the research question• Get – good examples of protocols– ideas from similar published studies– ideas from colleagues
• Use a checklist of items to include• Get the requested format
(grant application)
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Protocol outline
1. Presentation 2. Background and justifications 3. Objectives 4. Methods 5. Ethical considerations 6. Project management 7. Timetable 8. Resources 9. References10. Appendices
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1. Presentation
• Title– short, accurate, concise
• Investigators • Main centres• Steering committee (scientific board)• Summary of the protocol
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2. Background and justification
• Statement of problem, study justification importance of subject area
• magnitude, frequency gaps in existing knowledge principal questions to be addressed contribution of results to existing knowledge use of results dissemination of results
• Review relevant literature
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3. Objectives
• Should answer the study question• Should be S.M.A.R.T.– Specific–Measurable– Achievable/Accessible– Realistic/Relevant– Time-based/Timely
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3. Objectives
Principal objective• Must be achieved• Dictates design and methods
Secondary objectives• Of interest, but not essential
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Hypotheses
• Translation of the objectives in terms that allow statistical testing
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• Non S.M.A.R.T objective– To identify risk factors for HCV infection
Principal objective• To determine if sharing a haemodialysis machine with
a HCV infected patient is a risk factor for HCV infection
Secondary objective:• To identify failures in procedures
designed to prevent cross-infection via haemodialysis machines
3. Objectives example
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Hypothesis
“The incidence of HCV infection in haemodialysis patients is higher in patients sharing machines with HCV infected patients than in patients not sharing machines with an HCV infected patients”
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Protocol outline
1. Presentation2. Background and justifications3. Objectives4. Methods5. Ethical considerations6. Project management7. Timetable8. Resources9. References10. Appendices
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4. Methods
• Procedures to achieve objectives– what will be done?– how?
• Information used to judge validity
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4. Methods
• Study design cohort, case control, cross-sectional… brief justification
• Study population definition selection criteria for inclusion and exclusion mechanisms of recruitment accessibility, follow-up, representativeness
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4. Methods
• Sampling design (ref: lecture sampling) frame: district, household, persons,… method: random, cluster, stratified,… randomisation procedures replacement procedures (in case of refusal)
• Sample size (ref: lecture sample calculation) sample size, power calculations
based on principal objective feasibility
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Sample sizee.g. Options for case-control study on sporadic campylobacter
and food exposure
Prevalence of
exposure among
controls
Case: control ratio
Alpha error/ power
Odds ratio
to detect
Number of
cases
Number of
controls10% 1:2 5%/ 80% 2 223 446
10% 1:2 5%/ 80% 3 81 162
10% 1:2 5%/ 80% 4 48 96
10% 1:2 5%/ 80% 5 34 68
10% 1:2 5%/ 80% 6 27 54
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4. Methods
• Selection and definition exposures:
risk factors, protective factors, confounding factors outcomes:
definition of case, of control group
• Items to be measured– scales used
• e.g: legionella <=> car driving- Driving exposure: definition, quantification, categories- Legionella infection: case definition, control group definition
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CC study of sporadic cases
of Salmonella Enteritidis infections• Exposure
– consumption of custard
• Case– a person living in South-West Wales with
a laboratory confirmed infection due to S. Enteritidis in June and July 2011
• Case finding– through Public Health Laboratory; weekly notifications
• Control – persons living in SW Wales
in same neighborhood as cases
• Control finding – random selection of people using telephone directory
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MethodsData analysis plan
• Structured in terms of objectives• Hypotheses tested, dummy tables
Comparison of groups risk factors protective measures
Assessment of dose-response relationship for key exposures
Assessment of possible confounding factors / effect modifiers
• Statistical tests used, adjustment, stratification
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MethodsData analysis plan
• Define– indicators you will need to reach objectives
– data you will need to collect
• Better estimates of sample size for analysis of sub-groups
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MethodsData analysis
Dummy table:
Food specific attack rates of Salmonella infection
in a day care centre, Paris, May 2009
ill n
total n
AR %
RR 95%CI
ice-cream yes ice-cream no
fruit cake yes fruit cake no
pudding yes pudding no
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4. MethodsData collection
• How interview, observation, record review
• By whom interviewers: selection, training level of supervision
• Tools (ref: lecture “questionnaire design”) questionnaires, recording materials questionnaires: self or interviewer administered,
face-to-face or telephone interview
• Blind data collection• Procedures for taking samples
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4. MethodsData handling
• Coding (anonymisation) during data collection, afterwards? by whom?
• Processing software, hardware entry
• during the study, afterwards?• single entry, double entry?
• Validation and data cleaning
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4. MethodsPilot studies, pre-testing
• No study without pre-test
Feasibility of sampling
Data collection, measurement methods
Questionnaire
• Describe how to test
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4. MethodsLimitations
• Identification of potential sources of biases selection bias information bias misclassification bias interviewer bias
• How to deal with them possibilities for correcting how they will affect the results
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Protocol outline
1. Presentation 2. Background and justifications 3. Objectives 4. Methods 5. Ethical considerations 6. Project management 7. Timetable 8. Resources 9. References10. Appendices
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5. Ethical considerations
• Informed consent– translated in local lay language
• Confidentiality– coding data collection instruments
without identifier• Data storage and protection• Ethics committee
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6. Project management
• Participating institutes and persons
• Responsibilities and tasks of each partner
• Data ownership
• (Authorship)
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7. Timetable
Planning/organisation of the study• questionnaire design, recruitment, purchases• permission• obtain funding
Pilot study • time to do adjustments
Final study• data collection• analysis• presentation of results and write up
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8. Resources
• Extent of this section depends on target audience
• Specify available sources requested sources
• Keep budget reasonable detailed well justified
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9. References
• Limit number of references to key articles• Follow recommended style• Vancouver
www.library.soton.ac.uk/infoskills/vancouver.shtmlwww.transfusion.ca/new/bulletin/vancouver-style.html
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10. Appendices
• Methodological appendices• List of definitions• Questionnaires• Introductory letters to study participants• Informed consent forms…..
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Common problems
• Too ambitious: too many questions• Insufficient attention to literature
• Poor justification
why is it important to answer this question? what impact does it have on public health?
• Poorly formulated objectives• Inappropriate analysis• Inadequate description• Absence of pilot
Your task next week
• Create a study protocol in small groups• Present it to the plenary• Read the references during the weekend
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