Public Health 2 Flashcards

1
Q

What is a case control study

A
  • Looks at 2 sets of participants. One group has the condition you are interested in (the cases) and one group does not have it (the controls).
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2
Q

What are the advantages of a case-control study ?

A
  • Good for rare outcomes e.g. cancer
  • Quicker than cohort or intervention studies as outcome has already happened
  • Can investigate multiple exposures
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3
Q

What are the disadvantages of a case-control study ?

A
  • Difficulties finding controls to match cases
  • Prone to selection bias
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4
Q

What is a cohort study ?

A
  • Participants who do not have the outcome at baseline are followed over time to estimate the incidence of the outcome.
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5
Q

What are the advantages of a cohort study ?

A
  • Can follow-up a group with a rare exposure e.g. natural disaster
  • Good for common or multiple outcomes
  • Less risk of selection and recall bias
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6
Q

What are the disadvantages of a cohort study ?

A
  • Take a long time
  • Loss to follow up
  • Need a large sample size
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7
Q

Cross-Sectional Studies

A
  • Observational studies that analyse data from a population at a single point in time
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8
Q
  1. What are the advantages of a cross-sectional study ?
A
  • Relatively quick and cheap
  • Provide data on prevalence at a single point in time
  • Large sample size
  • Good for surveillance and public health planning
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9
Q

What are the disadvantages of a cross sectional study ?

A
  • Risk of reverse causality
  • Cannot measure incidence
  • Risk recall bias and non-response
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10
Q

What is a randomised control trial ?

A
  • Gold standard trial
  • A trial in which subjects are randomly assigned to one of two groups: one (the experimental group) receiving the intervention that is being tested, and the other (the comparison group or control) receiving an alternative (conventional) treatment.
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11
Q

What are the advantages of a randomised control trial ?

A
  • Low risk of bias and confounding
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12
Q

What are the disadvantages of a randomised control trial ?

A
  • Time consuming and expensive
  • Specific inclusion/exclusions criteria may mean the study is different from typical patients e.g. excludes elderly
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13
Q

How can an association between 2 things be explained ?

A
  • Chance
  • Bias
  • Confounding
  • Reverse causality
  • A true causal association
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14
Q

Selection bias can result from

A
  • Selection of study participants
  • Allocation of participants to different study groups
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15
Q

How can the selection of study participants and there allocation to different study groups impact selection bias ?

A
  • Non response e.g. are those who don’t respond likely to be from a specific group e.g. elderly
  • Loss to follow up e.g. are those who drop out more likely to be better or worse ?
  • Are those in the intervention group (or the cases) in some way from the controls other than the exposure in question
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16
Q

What types of information bias are there ?

A
  • Measurement
  • Observer
  • Recall Reporting
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17
Q

What types of Bias are there ?

A
  • Information
  • Selection
  • Publication
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18
Q

What is publication bias ?

A
  • Not all trial results are published
  • Papers with less positive results are less likely to be published
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19
Q

What is confounding ?

A
  • A situation in which estimates between an exposure and outcome is distorted because of the association of the exposure with another factor (confounder) that is also independently associated with the outcome
  • E.g. More shark attacks while there are more ice cream sales
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20
Q

Reverse causality

A
  • Refers to the situation when an association between an exposure and an outcome could be due to the outcome causing the exposure rather than the exposure causing the outcome
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21
Q

What is the Bradford-Hill Criteria for Causality

A
  • List of things required to say that one thing causes another
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22
Q

Features of the Bradford Hill Criteria

A
  • Strength
  • Consistency
  • Dose-response
  • Temporality
  • Plausibility
  • Reversibility
  • Coherence
  • Analogy
  • Specificity
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23
Q

Explain Strength from the Bradford Hill Criteria

A
  • Stronger the association between exposure and outcome
24
Q

Explain Consistency from the Bradford Hill Criteria

A
  • Same results observed from various studies in different geographical settings
25
Q

Explain Dose-response from the Bradford Hill Criteria

A
  • The increase risk of outcome increases alongside increased exposure
26
Q

Explain Temporality from the Bradford Hill Criteria

A
  • Exposure occurs prior to outcome
27
Q

Explain Plausibility from the Bradford Hill Criteria

A
  • Reasonable biological mechanism
28
Q

Explain Reversibility from the Bradford Hill Criteria

A
  • Intervention to reduce/remove the exposure eliminated/reduces outcome
29
Q

Explain Coherence from the Bradford Hill Criteria

A
  • Logical consistency with other information
30
Q

Explain Analogy from the Bradford Hill Criteria

A
  • Similarity with other established cause-effect relationships
31
Q

Explain Specificity from the Bradford Hill Criteria

A
  • Relationship specific to outcome of interest
32
Q
  1. What is the purpose of screening ?
A
  • To identify apparently well individuals who have or are risk of developing a particular disease so that you can have a real impact on the outcome
33
Q
  1. What does cervical screening detect ?
A
  • Pre-cancerous dyskaryosis and treats it to prevent it developing into carcinoma of the cervix
34
Q
  1. Disadvantages of screening
A
  • Exposure of well individuals to distressing or harmful diagnostic tests e.g. colonoscopies to those with positive faecal occult
  • Detection and treatment of subclinical disease that would have never cause any problems e.g. non-aggressive prostate cancers in elderly men
  • Prevention interventions that may cause harm to the individual or population
35
Q
  1. What is sensitivity
A
  • The proportion of those with the disease who are correctly identified by the screening test
36
Q
  1. What is specificity ?
A
  • The proportion of people without the disease who are correctly excluded by the screening test
37
Q
  1. Positive predictive value
A
  • Proportion of people with a positive test result who actually have the disease
38
Q
  1. Negative predictive value
A
  • Proportion of people who have a negative test result who do not have the disease
39
Q
  1. What is the NHS criteria for a condition to screen for
A
  • Should be an important health condition e.g. 1/8 women will develop breast cancer
  • Epidemiology and natural history must be adequately understood
  • There should be detectable RF, disease markers, latent period and early symptomatic stage
40
Q
  1. What is the NHS criteria for a test used in screening ?
A
  • Simple, safe and valid
  • Distribution of test values in the target population should be known and a suitable cut-off level defined and agreed
  • The test should be acceptable to the population
41
Q
  1. What is the NHS criteria for a screening program ?
A
  • Screening should be ongoing
  • The cost of screening should be economically balanced to healthcare spending as a whole
42
Q
  1. What is the NHS criteria for a treatment secondary to a screening program ?
A
  • Effective intervention or treatment for patients with evidence that early treatment leads to better outcomes than late treatment
  • Agreed evidence based policies determining who should be offered the appropriate treatment
  • Clinical management of the condition and the patient outcomes should be optimized in all health care providers prior to participation in the programme
43
Q
  1. What is lead time bias
A
  • When a screening identifies an outcome earlier than it otherwise would have been identified resulting in an apparent increase in survival even if screening has no effect on the outcome
44
Q
  1. What is length lead bias
A
  • An overestimation of survival duration due to the relative excess of cases detected that are asymptomatically slowly progressing, while fast progressing cases are detected after giving symptoms
45
Q
  1. What are different approaches to a Health Needs Assessment
A
  • Epidemiological
  • Corporate
  • Comparative
46
Q
  1. What is does an epidemiological Health Needs Assessment consider ?
A
  • Defines the problem
  • Assesses the size of the problem e.g. incidence + prevalence
  • Services available for the issue are assessed
  • Assess if this is matching the evidence base for effectiveness of cost effectiveness
  • Assess the care – quality and outcome measures
  • Assess for any unmet need + any unneeded existing services
47
Q
  1. What are the advantages of an epidemiology health needs assessment ?
A
  • Uses existing data
  • Provides data on disease
  • Incidence/mortality/morbidity can be assessed
  • Can evaluate services by trends over time
48
Q
  1. Disadvantages of an epidemiological health needs assessment ?
A
  • Quality of data is variable
  • Data collected may not be the data required
  • Does not consider the felt needs or opinions/experiences of the people affected
49
Q
  1. What is involved in a corporate approach to a health needs assessment ?
A
  • Ask the local population what their health needs are
  • Use focus groups, interviews and public meetings etc.
  • Wide variety of stakeholders e.g. teachers, healthcare professionals, social workers, charity workers, local businesses, council workers and politicians
50
Q
A
51
Q
  1. What is involved in a corporate approach to a health needs assessment ?
A
  • Ask the local population what their health needs are
  • Use focus groups, interviews and public meetings etc.
  • Wide variety of stakeholders e.g. teachers, healthcare professionals, social workers, charity workers, local businesses, council workers and politicians
52
Q
  1. What are the advantages of a corporate health needs assessment ?
A
  • Based on the felt and expressed needs of the population in question
  • Recognize the detailed knowledge and experience of those working with the population
  • Takes into account a wide range of views
53
Q
  1. What is a comparative approach to a health needs assessment ?
A
  • Compare the health or healthcare provision of one population to another
  • Spatial (different towns) or social (e.g. age or social class)
  • Can compare health, service provision/utilization, health outcomes
54
Q
  1. What are the advantages of a comparative approach to a health needs assessment ?
A
  • Quick and cheap if data is available
  • Indicates whether health or services provision is better/worse than comparable areas (gives a measure of relative performance)
55
Q
  1. Disadvantages of a comparative approach to a health needs assessment ?
A
  • Data not available/high quality e.g. not able to find 2 comparable populations
  • Its possible that nether group is using the ideal services