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1 - Hadpop > All Topics > Flashcards

All Topics Flashcards

1
Q

What is prevalence?
What is it affected by?
What is point prevalence?

A

Number of current cases at a given moment.
Increased by prolonging lives of sufferers.
Decreased by cures and deaths.
No of sufferers/No at risk

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2
Q

What is the crude death rate?

What is the age-specific death rate?

A

No of deaths per 1000 population

No of deaths per 1000 in an age group

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3
Q

What are the four disadvantages of case controlled studies?

A
  • Only estimates relative risk
  • No absolute incidence rates
  • Often prone to recall and selection bias
  • Can’t be sure exposure preceeds outcome
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4
Q

What is the incidence?

How do you calculate the incidence rate?

A

No. of new cases in a given time
Rate=number of new cases/person-years
Person-years=Number of people observed x Number of years observed

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5
Q

What three things can apparent associations results from?

A
  • Chance
  • Bias: Selection and Information Bias
  • Confounders
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6
Q

What are Confidence Intervals?How do you calculate them?

A

Values you can be 95% sure the true value lies between.

  • Upper = Observed x error factor
  • Lower = Observed/error factor
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7
Q

What are the 6 uses of mortality data?

A
  • Identifies cause of death to analyse patterns
  • Identifies health problems to inform services
  • Uses as incidence date for rapid diseases
  • Errors from omissions
  • Incorrect diagnoses
  • ‘Fashions’ in diagnosis
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8
Q

State and define the fertility determinants (fertility, fecundity, conceptions)
What is fertility increased and decreased by?

A

Fecundity = Physical ability to reproduces
Fertility = Realisation of fecundity
Conceptions = Live births + miscarriages + abortions
Increased by sexual activity + economic climate
Decreased by contraception and abortions

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9
Q

What is publication bias?

A

Studies with significant/favourable results are more likely to be published

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10
Q

What are the disadvantages of using historical controls? (3)

A
  • May have been treated differently
  • Less information about controls makes confounder adjustment difficult
  • Comparison with patients can overestimate the benefits of a new treatment
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11
Q

What are population estimates?

A

Applying what’s known abouts births, deaths and migrations to the present population

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12
Q

What are the characteristics of the ideal outcome? (12, but divide into 6 groups of two)

A

Appropriate: to patient, clinician, society
Valid: reasonably linked to treatments compared
Specific
Reliable: different people in different settings with same results
Simple and sustainable: repeatable
Cheap and timely: not expensive or long

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13
Q

What are the four advantages of case-controlled?

A
  • Study rare diseases
  • Study range of exposures
  • Cheap
  • Quick
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14
Q

What is the paradox of the commons, you sexy beast?

A

The principal that the optimum stratagey from an individual is not the optimum strategy for the community?

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15
Q

Why are there losses to follow up in studies? How can they be minimised? (four)

A

Clinical condition may necessitate removal or may choose to leave

  • Make follow up practical and convenient
  • Make clear commitment involved at start of study
  • Avoid coercion
  • Maintain contact
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16
Q

What are the three types of data?

A

Binary exposure
Several categories
Continuous

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17
Q

What is a case controlled study?

A

Classify on the basis of disease and the compare exposure status

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18
Q

What three factors contribute to population size?

A

Births, deaths and migration

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19
Q

What are the three types of blinding?
What are its benefits?
What are its difficulties?

A

Single, double and triple
Benefits = Avoids bias
Difficulties = Surgery, lifestyle interventions

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20
Q

What are observed quantities?
What is random variation?
What is affected by random variation to produce observed quantities?

A

Values that depart from their true value via random variation e.g. incidence, prevalence

Fluctuations in disease patterns that can’t be explained by systematic causes

True underlying tendencies

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21
Q

What is systematic variation?
How can it be used?
What is the problem with it?

A

Risk varies systematically throughout population
Can give clues as to cause of disease
Can confound relationships between 2 variables

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22
Q

What are the seven disadvantages to cohort studies?

A 
Resource intensive
Time consuming
Expensive 
Risk of high number of loss --> Survivor bias
Ethical dilemmas
Can't study rare diseases
Difficulty with confounding variable
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23
Q

What is the problem with incidence and prevalence?

A

They assume that all members of a population run the same rish, which they don’t

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24
Q

Why use random allocation when designing studies?

A

Minimise selection biase and confounders

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25
Q

What is a confounder?

How do you minimise them?

A

Affects both exposure and outcome, but does not lie on causal pathway
Matching using important confounders e.g. Age, Sex and ethnicity

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26
Q

What is the primary outcome?What is the secondary outcome?

A

Sample size

Side effects

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27
Q

What is selection bias?How do you minimise it?

A

Specifically selecting cases and controls so more likely to achieve desired result
Cases representative of cases
Controls representative of population

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28
Q

What are the ethical issues behind placebos? (3)

A
  • Deception
  • Should only be used when no standard treatment available for comparison
  • Patients should be fully informed that they may receive a placebo
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29
Q

What is the placebo effect?

A

Comparison of treatment to non-treatment

-Measure of the attitude change to the illness itself by the pure thought it being treated

30
Q

What are population projections?

A

Applying future estimates of births, deaths and migrations to future population estimations.

31
Q

What is causality?

A

Epidemiological addumption that no disease occurs at random and has preventable and causal factors

32
Q

Who writes the death certificate?What is in the death certificate? When must it be written?

A

Attending doctor
Cause of death
Within five days of death

33
Q

What are the 6 advantages of cohort studies?

A 
Rigorously defined disease + exposure
Study range of outcomes
Study rare exposures
Establish exposure preceeds outcome
Good for conditions that fluctuate with age

Prospective - detailed assement of exposure outcomes, personal characteristics and confounders.

34
Q

What is a hypothesis?

What is the null hypothesis?

A

A statement that an underlying tendency of scientific interest takes a particular value
States that there is no statistically significant different between 2 populations

35
Q

What is the meaning of :

  • Necessary
  • Sufficient
A

Necessary - Exposure must always preceed disease

Sufficient - Exposures capable of causing disease on its own

36
Q

What is the total period fertility rate?How is it calculated?

A

Average no of babies born to hypothetical woman between 15-44
Sum of age specific fertility rates

37
Q

What are the five advantages of clinical trials?

A
  • Provide reliable evidence of treatment efficacy and safety
  • Fair
  • Controlled
  • Reproducible
  • Intervention studies
38
Q

What is the standardised mortality ratio?How do you calculate it?

A

Compares the observed deaths in a population with the expected deaths of that age group, assuming the age-sex distributions are identical

No of observed deaths/No of expected deaths

39
Q

What are clinical trials?

A

Planned experiments involving patients which elucidates the most appropriate method of treatment for future patients with a given medical condition

40
Q

What is association?

A

Statistical dependance between 2 or more events, characteristics or other variables

41
Q

How many controls in case controlled study and why?

A

Increase in cases means increase in controls
Required to reduce error factor
Beyond 5 controls to cases, the decrease in error factor is disproportionate to the increase in costs of controls

42
Q

What is internal comparison?What observed value is calculated?

A

Between 2 groups within the cohort

Incidence rate ratio

43
Q

What is the point of clinical appraisal?

A

Distingus between good and bad evidence to provide optimal care for patiens

44
Q

What is the criteria for inferring causality? (9)

A 
Strength of association
Specificity of association 
Consistency of association
Coherence of theory
Biological plausability
Analogy 
Temporal sequence
Dose response 
Reversibility
45
Q

What is the incidence rate ratio?How is it calculated?What do its results indicate?

A

Comparison of incidence rates between 2 groups, varying in exposure
Rate A/Rate B >1 suggests increase risk in group A

46
Q

What is the crude birth rate?What is the general fertility rate?

A

No of babies born per 1000 population (live births)

Number of live births per 1000 women aged 15-44

47
Q

Why do we need a population perspective of medicine?

A

Look at large groups of people to discover causes of disease and evaluate preventative/curative measures

48
Q

What is external comparison?What is the observed value calculated?What are its limitations? (2)

A

Compare incidence within cohort with reference population

SMR-Limited data for reference population
-Reference and study pops may not be comparable due to selection bias and healthy worker bias

49
Q

What are the problems with hospital acquired infections? (3)How can HAIs be prevented? (3)

A 
Increase costs
Increase hospital stay
Cause deaths
Hand washing
Restrict anti-biotic usage
Cohort colonised and non colonised staff and patients together
50
Q

How do you interpret a 95% C.I?

A

Does the value of the null hypothesis lie between the Confidence Intervals?

  • Yes
  • Pt accept hypothesis
51
Q

Why is there variable study quality? (4)

How do you deal with this? (3)

A

Poor study design
Design protocol
Protocol implementation
Prone to bias + confounders

Define basic quality standard
Score each study
Incorporate into weighting

52
Q

What is a cohort study?What are the types?

A

Classify patients based on exposure and then follow up to look for outcome-Prospective - Exposure status and follow up-Retrospective - Exposure status and follow up based on historical records

53
Q

What are the 5 contentious issues associated with health care information use?

A 
Completeness/duplication
Accuracy
Confidentiality
Numerator/Denominator mismatch
Varying diagnosis of disease
54
Q

What is age sex standardisation?

Why use it?

A

A procedure that adjusts for age-sex differences in population structure, to provide a single summary measure

Age and sex are both factors that can confound disease risk

55
Q

What is health information used for? (3)

A

Identify health and healthcare needs
Monitor trends in disease
Monitor peformance in healthcare

56
Q

What is a census?

What information about the population does it produce?

A

Simultaneous recording of data by the government at a particular time, pertaining to all persons living in a particular territory
Population size and structure

57
Q

What are meta analyses?What observed value is calculated?

A

Quantitive synthesis of the results of 2 or more primary studies, that addressed the same hypothsis in the smae wayPooled estimate odds ratio

58
Q

What are forest plots?

A 
Squares = Individual ORs= Size x Weight
Lines = 95% CIs
Diamond = Pooled estimate
Centre = Pooled OR
Width = Pooled CI
Solid line = Null hypothesis
RCTs with OR>1 = greater survival odds
59
Q

Why are systematic reviews so credible? (5)

A 
Unbiased
Objective
Explicit
Transparent
Reproducible
60
Q

What is intention to treat analysis?

A

Everyone is included

More representative of population

61
Q

What are systematic reviews?

A

Overview of primary studies, which the synthesis can include meta-analyses

62
Q

Why are outcomes predefined?

A 
Prevents data dredging
Prevents repeat analyses
Sets data collection protocol
Provides agreed criteria for measurement
Assesment of outcomes
63
Q

What is as-treated analysis?

What is its problem?

A

Non-compliers excluded

  • 2 groups no longer random
  • Lost immunity to confounders
64
Q

What 2 methods are used for calculating pooled estimate OR?

A

Fixed-effect model: Studies estimate the same effect size

Random effect model: Studies estimate similar effect size

65
Q

What is a nested case controlled study?

A

Collection of data from an evolving exposure and outcome database of a propective cohort study

66
Q

What is a funnel plot?

A

Measure study size against measure of effect

Balanced funnel means no bias

67
Q

What are the steps in conduction of Randomised Control Trial?

A 
Identify cohort
Recruit participants
Consent
Maintain 
Allocate 
Assess
68
Q

What are the advantages of nested case-controlled over cohort and case-controlled studies?

A

Cohort: Collect more detailed information for a minority of participants
Case-controlled:
- Incidence rates can be defined
- Population for sampling of controls is already defined

69
Q

Define:

  1. Collective ethic
  2. Individual ethic
  3. Clinical equipoise
  4. Valid consent
A

1- All individuals have the right to safe and efficient treatment
2-RCTs go against beneficence, non-maleficence, autonomy and justice
3-Genuine ignorance of no better treatment
4-From a knowledgeable informant with appropriate information

70
Q

What is information bias?

A

Bias as a result of misclassification of exposure of outcomes.

71
Q

Information bias definition

A

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

1 - Hadpop (5 decks)

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