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Semester 1 > HaDPop > Flashcards

HaDPop Flashcards

1
Q

What is a census useful for?

A

Allocation of resources
Projections of populations
Trends in populations

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2
Q

What is crude birth rate?

A

Number of live births per 1000 population

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3
Q

What is general fertility rate?

A

Number of live births per 1000 fertile women aged 15-44

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4
Q

What is total period fertility rate?

A

Average number of children born to a hypothetical woman in her lifetime

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5
Q

What is the difference between fecundity and fertility?

A

Fecundity is the physical ability to reproduce whereas fertility is the realisation of this as births

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6
Q

What is age standardised death rate?

A

Number of deaths per 1000 in age group

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7
Q

What is standardised mortality rate?

A

Comparison of observed and expected death rates if the age-sex distribution is adjusted for

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8
Q

What is incidence?

A

Number of new cases a year

A rate b/cod the time dimension

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9
Q

How is incidence calculated?

A

New events/(person x time)

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10
Q

What is prevalence?

A

Number of people in a population with existing disease

Proportion

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11
Q

How is prevalence estimated?

A

Incidence x length of disease

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12
Q

How is incidence rate ratio calculated?

A

Exposed/unexposed

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13
Q

What are the different types of risk associated with rate and ratio?

A 
Rate = absolute
Ratio = relative
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14
Q

What is an observed value the best estimate of?

A

True/underlying tendency

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15
Q

What does a null hypothesis assume?

A

No difference b/w two outcomes

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16
Q

What does p>0.05 indicate?

A

Hypothesis can neither be rejected or accepted

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17
Q

What is the 95% confidence interval?

A

Range within which we can be 95% certain the true value of the underlying tendency lies

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18
Q

Is the observed value always in the 95% CI?

A

Yep

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19
Q

How is the confidence interval calculated?

A

Calculate observed value
Calculate error factor
Lower limit = observed/e.f.
Upper limit = observed x e.f.

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20
Q

How do you conduct a cohort study?

A

Recruit disease-free cohort –> follow over time –> incidence ratio –> calculate incidence rate ratio (relative risk)

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21
Q

What are the advantages of cohort studies over routinely available data?

A

Study unusual exposures and personal characteristics
More detailed info on outcomes and exposures
Additional data on confounding factors can be collected after trail starts

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22
Q

What is a census?

A

Simultaneous recording of demographic data to all persons in a defined area

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23
Q

How is a concurrent/prospective cohort study conducted?

A

Recruit outcome free individuals and classify by exposure status –> follow up counting p-y and cases

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24
Q

When can data collection be carried out for a prospective cohort study?

A

Immediately or delayed

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25
Q

Why may there be a delayed start to a concurrent cohort study?

A

Organisation

Ensure participants are disease free

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26
Q

How is a retrospective/historical cohort study conducted?

A

Recruit disease free individuals and classify on initial exposure status –> count p-y and cases using data records

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27
Q

Can a historical cohort study be continued into a concurrent study?

A

Yes

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28
Q

What is internal comparison in a cohort study?

A

Comparison of sub-cohorts

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29
Q

Why may there be a large error factor in an internal comparison?

A

Sub cohorts may be radically different sizes

Sub cohorts may not be comparable due to confounding

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30
Q

What is used to numerically evaluate internal comparison?

A

IRR

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31
Q

What must be large to give a small error factor when conducted an internal comparison?

A

Both sub-cohorts

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32
Q

What is external comparison in a cohort study?

A

Comparison of a cohort with a reference population after standardisation methods have been used

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33
Q

What is used to compare numerical data in external comparison of cohort studies?

A

SMR

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34
Q

What is used to calculate the expected cases in the reference population for an SMR in external comparison of a cohort study?

A

Lexis diagram

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35
Q

What determines the size of the SMR in external comparison of cohort studies?

A

The smallest cohort

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36
Q

Why is the error factor for internal comparisons larger than for external comparisons in cohort studies?

A 
IRR = two terms in e.f. expression
SMR = one term
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37
Q

Is the confidence interval larger in an external or internal comparison of a cohort study?

A

Larger for IRR therefore larger in internal

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38
Q

What are the disadvantages of an external comparison in a cohort study?

A

Limited data for reference population
Often no incidence data
Usually compromise with mortality data
Selection bias - healthy worker effect

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39
Q

What is the healthy worker effect?

A

Occupational cohorts yield SMRs

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40
Q

What are the advantages of using a concurrent cohort study?

A

Allow detailed and prospective assessment of exposure, outcomes and confounders

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41
Q

What type of conditions are cohort studies better suited to?

A

Fluctuate randomly or systematically w/age

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42
Q

What advantages do cohort studies have over case-control?

A

Better for studying a range of outcomes
Better for studying a rare exposure
Establishes exposure preceded outcomes

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43
Q

What are the disadvantages of using a cohort study?

A 
Large and resource intensive
Take a long time
Survivor bias to follow up
Ethical dilemma and political change effects due to long duration
Not good for rare outcomes
Difficulty w/confounding
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44
Q

How is a case-control study conducted?

A

Identify group of cases
Ascertain previous exposure status of everyone
Compare level of exposure in cases and controls

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45
Q

What numerical method is used to examine case-control studies?

A

Odds ratio

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46
Q

How is an odds ratio calculated?

A

ad/cb

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47
Q

What is the rare disease assumption?

A

If both unexposed and exposed case numbers are much smaller than control numbers we can assume IRR ~= ad/cb

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48
Q

How does a case-control study compare outcomes?

A

Based on outcome status

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49
Q

How does a cohort study compare outcomes?

A

Based on exposure status

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50
Q

What is the economic advantage of case-control studies over cohort?

A

Quicker therefore cheaper

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51
Q

Is a cohort study or case-control study better for rare exposures?

A

Cohort

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52
Q

Is a cohort study or case-control study better for rare outcomes or diseases?

A

Case-control

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53
Q

Which two types of bias are case-control studies prone to?

A

Selection

Information

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54
Q

How does a cohort study limit bias?

A

By ascertaining exposure status

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55
Q

What is a nested case-control study?

A

Collection of data from evolving outcome and exposure database of concurrent cohort study

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56
Q

Which type of study can directly measure incidence?

A

Cohort

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57
Q

What factors suggest a case-control study would be suitable?

A

Rare diseases
Look into many different exposures at once
Absolute incidence rates not needed

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58
Q

Why can you not use an IRR to evaluate a case-control study?

A

Cannot be sure you have the right denominator

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59
Q

What is the precision of an OR affected by which does not affect an IRR?

A

Number of healthy people

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60
Q

How many times more controls than cases do you typically use in a case-control study?

A

5

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61
Q

What gives the largest error factor in calculating the odds ratio for a case-control study?

A

Smallest of a,b,c or d

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62
Q

What is the most difficult aspect of a case-control study to control?

A

Selection bias - participants not representative of general population

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63
Q

Which bias are case-control studies susceptible to?

A

Selection
Recall
Systematic

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64
Q

Why are case-control studies subject to recall bias?

A

Exposure status is incorrectly determined due to looking back at history to determine exposure

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65
Q

How does systematic bias arise in case-control studies?

A

Assessor bias

Data collection methods differ

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66
Q

How are confounders removed from case-control studies?

A

Match up cases and controls with similar details

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67
Q

What is a necessary exposure?

A

Always precedes disease

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68
Q

What is a sufficient exposure?

A

Can cause disease in its own

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69
Q

In epidemiology, what is a cause?

A

Exposure of factor that increases the probability of disease

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70
Q

What can apparent associations arise from?

A 
Chance
Selection bias
Information bias
Confounding
Reverse causality
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71
Q

What is selection bias?

A

Error due to systematic differences in the characteristics of the groups being studied due to differences in the way they were selected

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72
Q

What is information bias?

A

Error due to systematic differences in the measurement or classification of subjects in the group being studied

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73
Q

What is confounding?

A

Something which has an effect on both the exposure and the outcome

74
Q

What is reverse causality?

A

Cause-effect relationship exists in wrong direction

75
Q

What is association when referring to epidemiology?

A

Statistical dependence b/w 2 or more events

76
Q

Which types of studies are classed as analytical studies?

A

Cohort

Case-control

77
Q

Which study is an example of an experimental study?

A

Random control trial

78
Q

As well as analytical studies, what do observational studies encompass?

A

Prevalence studies

79
Q

What were Henle-Koch’s postulates?

A

Agent not found in other disease cases
Agent in every case by isolation in pure culture
Once isolated, agent can reproduce and be recovered from experimental disease

80
Q

Which is the strongest Bradford-Hill criterion?

A

Reversibility

81
Q

What are the 9 Bradford Hill Criteria for inferring causality?

A 
Reversibility
Coherence of theory
Specificity of association
Analogy
Consistency of association
Biological plausibility
Dose response
Temporal sequence
Strength of association
82
Q

What is reversibility?

A

Removal/prevention of putative factor –> reduced/non existent risk of outcome

83
Q

What is specificity of association?

A

Association specific to exposure - outcome association more likely to be causal

84
Q

How does analogy infer causality?

A

If one exists –> more plausible

85
Q

What is consistency of association?

A

Demonstrated by different studies, different people, different times and different places more likely to be causal as unlikely to be explained by same confounding or bias

86
Q

What is biological plausibility?

A

Biologically plausible mechanism infers causality

87
Q

What is biological plausibility limited by?

A

Current knowledge

88
Q

What is does response?

A

Varying exposure gives varying outcome - confounding/bias unlikely to operate at same degree

89
Q

What is temporal sequence?

A

Association in which putative factor precedes outcome more likely to be causal

90
Q

What is strength of association?

A

Strong association –> more likely to be causal

91
Q

What is coherence of theory?

A

Conforms w/current knowledge and theory

92
Q

What are 2 fundamental assumptions in any epidemiological investigation into a disease?

A

Disease does not occur at random

Disease has causal and preventable factors that can be identified through systematic investigation

93
Q

What are the four steps of epidemiological reasoning?

A

Hypothesis
Analytical study
Observed association - exclude alternative associations
Does statistical association represent cause-effect?

94
Q

What scheme is used for the assessment of causation?

A

Description of the evidence
Internal validity: non-causal associations
Internal validity: features of causality
External validity: generalisation of results
Comparisons w/other evidence

95
Q

What 3 questions are considered when assessing non-causal associations in internal validity?

A

Has methodology minimised bias?
Any potential confounders?
How likely is it results are due to chance?

96
Q

What are four questions considered when assessing features of causality?

A

Strong relationship?
Dose response relationship?
Specificity of association?
Correct time relation/reverse causality?

97
Q

What is considered using the study results during generalisation of results?

A

Applied to source population
Applied to other population
Relevant to your population?

98
Q

What is asked when comparing results with other evidence when assessing causation?

A

Consistent w/more powerful study design?
Specificity?
Biological mechanism?

99
Q

What is the basic reproductive rate of infection, R?

A

R = B x D

B = transmission coefficient
D = time period of infectivity
100
Q

What just a clinical trial be?

A

Fair - unbiased w/out confounding
Controlled - comparison of interventions
Reproducible - in experimental conditions

101
Q

What aspect of a RCT that differs from a cohort study makes the RCT unethical?

A

Treatment allocated by trial investigator so the investigator is taking part in the trial

102
Q

What is efficacy when talking about health care interventions?

A

Ability to improve the health of a defined group under specific conditions

103
Q

What are the disadvantages of non-randomised clinical trials?

A

Allocation bias

Known and unknown confounding

104
Q

How could clinicians cause allocation bias in a non-randomised clinical trial?

A

They would not include patients with multiple morbidities with the new treatment

105
Q

What are problems caused by comparison with historical controls in NRCTs?

A

Selection less rigorous
Treated differently from ‘new treatment’ group
Unable to control for confounders
Almost always overestimate benefit of new treatments
Less information available on bias and confounders

106
Q

What is compared in a NRCT?

A

New treatment v.s. standard treatment

107
Q

What are the three main steps involved in RCT?

A

Define
Conduct
Comparison

108
Q

What must be defined in a RCT?

A 
Disease
Treatments to be compared
Outcomes to be measured
Possible bias and confounders
Patients eligible for trial
Patients to be excluded
109
Q

How is an RCT conducted?

A 
Identify eligible patient source and invite
Consent willing patients
Fairly allocate to treatments
Minimise losses and maximise compliance
Follow up identically
110
Q

What is considered in the comparison stage of an RCT?

A

Observed difference? –> arisen by chance?
Big observed difference?
Is observed difference attributable to treatment?

111
Q

How does random allocation minimise confounding?

A

Treatments groups are likely to be similar in size and characteristics by chance

112
Q

How can random allocation of treatment be achieved?

A

Toss a coin
Random number tables
Computer generated random number

113
Q

How can knowing the treatment allocation bias a trial?

A

Patient alters behaviour
Clinician alters treatment/care/interest (non-treatment effects)
Investigator alters approach when measuring/assessing (measurement bias)

114
Q

What is the difference between single, double and triple blinding?

A 
Single = patient/clinician/assessor does not know allocation
Double = two of above do not know
Triple = non of above know
115
Q

How is blinding achieved?

A

Aim to make treatments appear identical in every way

116
Q

What treatments can blinding be difficult for when using an RCT?

A 
Surgery
Psychotherapy v.s. antidepressant
Alternative medicine
Lifestyle interventions
Prevention programmes
117
Q

What is the placebo effect?

A

Knowing you are receiving a ‘new’ treatment is enough to make you feel better

118
Q

What are the ethical implications of the placebo effect?

A

Placebo = deception
Only used when no standard treatment available
Must inform patient is receiving a placebo

119
Q

What criteria must suitable outcome measures for clinical trials meet?

A 
Appropriate and relevant
Valid and attributable
Sensitive and specific
Reliable and robust
Simple and sustainable
Cheap and timely
120
Q

What are outcome measures?

A

Defined before start of trial
Prevent data dredging
Protocol for data collection
Agreed criteria for measurement and outcome assessment

121
Q

What do secondary outcomes of clinical trials include?

A

Occurrence of side-effects

Other outcomes of interest

122
Q

How many primary outcomes is preferable in a clinical trial?

A

One

123
Q

What outcome measures do you need during a clinical trial?

A

Baseline
During
Final

124
Q

What three characteristics do outcome measures have?

A

Patient focussed
Clinically defined
Patho-physiological

125
Q

What can cause non-compliance?

A 
Patient believes treatment is not working
Prefer other treatment
CBA
Misunderstood instructions
Dislike treatment
126
Q

How are losses to follow up minimised?

A

Make follow up practical and convenient
Be honest about commitment
Avoid coercion
Maintain participant contact

127
Q

What is an explanatory trial?

A

‘As treated’

Non compilers excluded

128
Q

What does an explanatory trial establish?

A

Physiological potency

129
Q

What is not preserved in an explanatory trial?

A

Random allocation - no longer immune to confounding

130
Q

What is a pragmatic trial?

A

‘Intention to treat’
If participants don’t like taking drug then future patients won’t either
Non-compliers included

131
Q

What is preserved in a pragmatic trial?

A

Randomisation - no confounding problems

132
Q

What was the declaration of Helsinki (2000)?

A

‘The health of my patient will be my first consideration’

133
Q

What are considerations of the individual ethic in an RCT?

A 
Principle of autonomy
Principle of justice
Principle of nonmaleficence
Principle of beneficence
RCTs do not guarantee benefit - may result in harm as for benefit of future patients, not participants
RCTs allocate treatment by chance
134
Q

What five issues should be considered for a clinical trial to be regarded as ethical?

A 
Clinical equipoise
Scientifically robust
Ethical recruitment
Valid consent
Voluntariness
135
Q

What is clinical equipoise?

A

Reasonable uncertainty/genuine ignorance about better treatment

136
Q

What does clinical equipoise allow?

A

Valid consent

137
Q

What are the issues with clinical equipoise?

A

Uncertainty of individual clinician or scientific community
“Reasonable uncertainty”?
“Better” for patient or society?

138
Q

What makes a clinical trial scientifically robust?

A 
Relevant/important issue
Asks valid question
Appropriate study design and protocol
Potential to reach sound conclusions
Justify comparator/placebo treatment
Acceptable risks of harm
Provision for safety and well being monitoring
Arrangements for appropriate reporting and publication
139
Q

What is inappropriate inclusion in ethical recruitment?

A

Participants unlikely to benefit
High risk participants
Participants likely to be excluded

140
Q

What is inappropriate exclusion in ethical recruitment?

A

People who differ from an ideal homogenous group

People difficult to get valid consent from

141
Q

What is needed for valid consent?

A 
Knowledgable informant
Appropriate information
Cooling off period
Informed participant
Competent decision-maker
Legitimate authoriser
142
Q

Does a signed consent form equate with valid consent?

A

No!

143
Q

What is Voluntariness?

A

Decision to participate is free from coercion or manipulation

144
Q

What is the role of the Research Ethics Committee?

A

Ensuring dignity, rights, safety and well-being of participants is the primary consideration in any research study

145
Q

Who manages research governance in clinical trials?

A

NHS Trust

146
Q

Who governs financial management of clinical trials?

A

PCT

147
Q

Who governs resource implication of clinical trials?

A

R+D office

148
Q

Why are literature reviews using expert reviews biased and subjective?

A

Have to make the same assumptions as the expert, can’t be sure you’d reach the same conclusions

149
Q

Why is a literature review using systematic reviews unbiased and objective?

A

Explicit assumptions
Transparent methodology
Reproducible

150
Q

When is a systematic review used?

A

When an overview of primary studies that used explicit and reproducible methods is needed

151
Q

What should a systematic review set out to identify as completely as possible?

A

All relevant evidence, published or not that meet certain predefined criteria with clear aims

152
Q

What should a systematic review analyse carefully?

A

Results of all studies identified

Quality of all studies identified

153
Q

What does a systematic review include explicit statements about?

A

Types of outcome measures
Types of interventions
Types of participants
Types of study

154
Q

What does a systematic review investigate?

A

Clearly focused question with a single outcome

155
Q

What do you have to use to carry out a systematic literature search?

A

Professional researchers

156
Q

What three criteria must a systematic review meet?

A

Explicit
Transparent
Reproducible

157
Q

What is a meta-analysis?

A

Quantitative synthesis of the results of two or more primary studies that addressed the same hypothesis in the same way

158
Q

What is the purpose of a meta-analysis?

A

Facilitate synthesis of a large number of study results
Systematically collate study results
Reduce problems of interpretation due to variations in sampling
Quantify effect sizes and their uncertainty as a pooled estimate

159
Q

What 4 quality criterion must be met in order for a meta analysis to be used?

A

Compilation of a complete set of studies
Identification of common variable or category definition
Standardised data extraction
Analysis allowing for sources of variation

160
Q

What numerical analysis is carried out using a computer programme in meta analysis?

A

ORs and 95% CI for all and pooled data

Pooled estimate OR

161
Q

What are studies in a meta analysis weighted according to?

A

Size

OR uncertainty

162
Q

How does a small error factor affect the weighting of a study in meta analysis?

A

Increases it

163
Q

How are the individual odds ratios in a meta analysis displayed on a forest plot?

A

Square with size in proportion to its weighting

Horizontal line indicates 95% CI

164
Q

What does the diamond on a Forest plot represent?

A

Pooled estimate
Centre indicates pooled odds ratio
Width represents pooled 95% CI

165
Q

What is the vertical line on a Forest plot?

A

Null hypothesis odds ratio

166
Q

What does it mean if the 95% CI toughest the null hypothesis line?

A

Results are not statistically significant

167
Q

What are the two common difficulties in systematic reviews and meta analysis?

A

Heterogeneity b/w studies

Variable quality of studies

168
Q

What is the fixed effects model?

A

Assumes studies are estimating exactly the same effect size by measuring one true value using any resources

169
Q

What is the random effects model?

A

Assumes estimating similar but not same effect size by trying to calculate mean for all effects

170
Q

What can be used to analyse variation between heterogenous studies?

A

Sub-group analysis

171
Q

What can the random effects model account for but not explain?

A

Variation

172
Q

In which effects model in systematic review and meta analysis is the 95% CI wider?

A

Random

173
Q

Is weighting more equal in random effects or fixed effects model?

A

Random

174
Q

Why does the hypothesis test for heterogeneity have low statistical power?

A

Uses 10% significance for p value

175
Q

What can cause variable quality of studies in systematic review and meta analysis?

A

Poor study design
Poor design protocol
Poor protocol implementation

176
Q

List the types of study in order of susceptibility to bias and confounding starting with the least susceptible.

A

RCTs
NRCTs
Cohort
Case-control

177
Q

How is variable quality of studies in systematic review and meta analysis approached?

A

Define basic quality standard and only include studies that satisfy it or weight studies on how well they fit it

178
Q

What is the effect of publication bias?

A

Studies w/ statistically significant or favourable results are more likely to be published leading to biased selection for systematic review and meta analysis

179
Q

What size of study is more susceptible to publication bias?

A

Small - bug are almost always published

180
Q

How can publication bias be analysed in a systematic review?

A

Check meta analysis
Funnel plot
Use weak statistical test

181
Q

What will the funnel plot of a more reliable systematic review which is less affected by publication bias look like?

A

Closer to central dotted line with studies equidistant from line

182
Q

What kind of stats analysis is usually better to assess variable quality of studies in a systematic review or meta analysis?

A

Simple

Semester 1 (7 decks)

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