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Semester 1 - HADPOP > HADPOP Guide > Flashcards

HADPOP Guide 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:
Selction, Information
-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

What is fertility increased and decreased by?

A

Fecundity - Physical ability to reproduces
Fertility - Realisation of fecundity
Conceptions - Liver 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 adjusment 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

Avoids bias

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 disesae

Can confound relationships between 2 variables

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22
Q

What are the seven disadvantages to cohort studies?

Really Tired Elephants Share Ears with Randy Creeps

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

Compariosn 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 ran 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 worman 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 efficacu 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
Consitency of association

Coherence of theory
Analogy
Biological plausability

Reversibility
Temporal sequence
Dose response

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
<1 suggests increase in risk in group B

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

How do you calculate odds ratio?

A

—————-Cases—-Controls
Exposed—–A————-B—-
Unexposed–C————D

AxD/BxC = Odds of being exposed (cases)/odds of being exposed (controls)

50
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 useage
Cohort colonised and non colonised staff and patients together

51
Q

How do you interpret a 95% C.I?

A

Does the value of the null hypothesis lie between the CIs?

  • Yes
  • Pt accept hypothesis
52
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

53
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
54
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
55
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

56
Q

What is health information used for? (3)

A

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

57
Q

What is a cencus?

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

58
Q

(S9 +)
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 way

Pooled estimate odds ratio

59
Q

(S9 +)

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
60
Q

(S9 +)

Why are systematic reviews so credible? (5)

A 
Unbiased
Objective
Explicit
Transparent
Reproducible
61
Q

(S9 +)

What is intention to treat analysis?

A

Everyone is included

More representative of population

62
Q

(S9 +)

What are systematic reviews?

A

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

63
Q

Why are outcomes predefined? (S9 +)

A 
Prevents data dredging
Prevents repeat analyses
Sets data collection protocol
Provides agreed criteria for measurement
Assesment of outcomes
64
Q

What is as-treated analysis? (S9 +)

What is its problem?

A

Non-compliers excluded

  • 2 groups no longer random
  • Lost immunity to confounders
65
Q

What 2 methods are used for calculating pooled estimate OR? (S9 +)

A

Fixed-effect model:
Studies estimate the same effect size

Random effect model:
Studies estimate similar effect size

66
Q

What is a nested case controlled study? (S9 +)

A

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

67
Q

What is a funnel plot? (S9 +)

A

Measure study size against measure of effect

Balanced funnel means no bias

68
Q

What are the steps in conduction of Randomised Control Trial? (S9 +)

A 
Identify
Recruit
Consent
Maintain
Allocate
Assess
69
Q

What are the advantages of nested case-controlled over cohort and case-controlled studies? (S9 +)

A

Cohort:
Collect more detailed inmfromation for a minority of participants

Case-controlled:

  • Incidence rates can be defined
  • Population for sampling of controls is already defined
70
Q 
Define: (S9 +)
Collective ethic - 1
Individual ethic  - 2
Clinical equipoise -3
Valid consent -4
A

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

71
Q

What is information bias?

A

Bias as a result of misclassification of exposure of outcomes. Can be differential or non-differential.

72
Q

Information bias definition

A

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

Semester 1 - HADPOP (5 decks)

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