Use of Whole Population Registers: Advantages and Disadvantages.
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Transcript of Use of Whole Population Registers: Advantages and Disadvantages.
![Page 1: Use of Whole Population Registers: Advantages and Disadvantages.](https://reader035.fdocuments.us/reader035/viewer/2022062404/551a07e7550346ad578b45b8/html5/thumbnails/1.jpg)
Use of Whole Population Registers:
Advantages and Disadvantages
![Page 2: Use of Whole Population Registers: Advantages and Disadvantages.](https://reader035.fdocuments.us/reader035/viewer/2022062404/551a07e7550346ad578b45b8/html5/thumbnails/2.jpg)
Problems in Observational Studies
• Who gets included?
• Who gets lost?
• How to ensure completeness of recruitment?
• How to standardise assessment?
• How to collect routinely gathered data fit for purpose?
• Source of control group(s)?
![Page 3: Use of Whole Population Registers: Advantages and Disadvantages.](https://reader035.fdocuments.us/reader035/viewer/2022062404/551a07e7550346ad578b45b8/html5/thumbnails/3.jpg)
Threats
• Internal validity
• External validity
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Problem with:‘my clinical series’
• Who are your patients?
• Which patients could you have included?
• Which patients have you lost– And why?
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Issue of Catchment population
Your area
Your Clinic
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Issue of Catchment population
Your area
Your Clinic
Other clinics
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Issue of Catchment population
Your area
Your Clinic
Other Clinic
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Issue of Catchment population
Your area
Your Clinic
Other Clinic ???
![Page 9: Use of Whole Population Registers: Advantages and Disadvantages.](https://reader035.fdocuments.us/reader035/viewer/2022062404/551a07e7550346ad578b45b8/html5/thumbnails/9.jpg)
Issue of Catchment population
Your area
Your Clinic
Other Clinic???
![Page 10: Use of Whole Population Registers: Advantages and Disadvantages.](https://reader035.fdocuments.us/reader035/viewer/2022062404/551a07e7550346ad578b45b8/html5/thumbnails/10.jpg)
Does it matter
• May or may not?
• Selection factors related to:– Disease severity– Access– Costs– Education– Co-morbidity– Waiting time etc
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Who gets lost:The issue of left censorship
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2001 2007
Recruiting patients from clinic
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2001 2007
Recruiting patients from clinic:
Attenders between January 2003 and December 2004
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2001 2007
Recruiting patients from clinic:
Attenders between January 2003 and December 2004
![Page 15: Use of Whole Population Registers: Advantages and Disadvantages.](https://reader035.fdocuments.us/reader035/viewer/2022062404/551a07e7550346ad578b45b8/html5/thumbnails/15.jpg)
2001 2007
Recruiting patients from clinic:
Attenders between January 2003 and December 2004
![Page 16: Use of Whole Population Registers: Advantages and Disadvantages.](https://reader035.fdocuments.us/reader035/viewer/2022062404/551a07e7550346ad578b45b8/html5/thumbnails/16.jpg)
2001 2007
Recruiting patients from clinic:
Attenders between January 2003 and December 2004
![Page 17: Use of Whole Population Registers: Advantages and Disadvantages.](https://reader035.fdocuments.us/reader035/viewer/2022062404/551a07e7550346ad578b45b8/html5/thumbnails/17.jpg)
2001 2007
Recruiting patients from clinic:
Attenders between January 2003 and December 2004
? Died
? Remitted
? Lost hope
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What is the message?
Recruiting current attenders is biassed
towards:
• Survivors
• Continuing problems
• Specific socio-economic groups
• Treatment responders/non-responders
• People who like you!
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Ideal
• Whole population
• Captured at time of onset (inception cohort)
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How to ascertain cases from whole population?
Fix population:
1. Health plan coverage
2. Other special group (eg Nurses)
3. Geographical
(beware of selection factors for 1 and 2)
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Self Care
Primary Care
Secondary
Care
Tertiary Care
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Threshold vary:
• Disease severity
• Socio-economic/education
• Availability of care
• Psychological factors
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Minimum entry severity point has to be
primary care
BUT
Still legitimate to use other cut offs if external validity
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Choices for ascertainment
• Detect diagnosed cases based on database search and chart review– Administrative database (eg Pharmex, GPRD)– Institutional database (eg Mayo Clinic)
• Set up prospective system
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Use of diagnosed cases
• Cheap
• Quick
• Will allow retrospective recruitment
• Not relying on compliance
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Prospective system
• Accuracy of data
• Reliability of data
• Timeliness of data
• Build in appropriate follow up
• ?consent/ethics
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Attrition:Losses from cohort
Why:
• Die
• Get better
• Deteriorate (DNA)
• Lose interest
• Change doctor
• Move
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In practice:
Losses from cohort are greater threat to
validity that failure to recruit
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Minimise attrition• Engaging subjects with research
– Frequent contact– Feedback– Consent
• Baseline data on key informants• Consent to access medical and other
records• Linkage to other datasets• Subjects do opt in