Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

PHM 101 Basic Epidemiology > Ch 8 & 9 intervention studies, prevention strategies > Flashcards

Ch 8 & 9 intervention studies, prevention strategies Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards Psychology 101 flashcards Chemistry 101 flashcards Biology 101 flashcards Organic Chemistry 101 flashcards Sociology 101 flashcards
1
Q

The only way to determine causality is through what type of study?

A

Intervention study.

Analytical studies only show causal “association”.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is manipulated in an intervention study? what is the purpose of changing that variable?

A

investigators manipulate the exposure to see what effect it has on the outcome.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is the ideal intervention study design and why?

A

randomized control trial because it can reduce bias and confounding

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

• recognize when non-randomized intervention studies may be appropriate

What types of controls will be used instead?

A
  • intervention is very complex
  • evidence required on a large scale
  • ethical concerns with RCTs
  • historical control
  • geographical control
  • opportunistic control
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what does an intervention study measure?

A

the association between an outcome and exposure to a specific intervention

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what form can this intervention take on?

A
  • prevention of exposure to those at risk (insecticide infused nets to prevent malaria)
  • tx to prevent death and severity in those affected (rx to prevent worsening of dz)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what form can this intervention take on?

A
  • prevention of exposure to those at risk (insecticide infused nets to prevent malaria)
  • tx to prevent death and severity in those affected (rx to prevent worsening of dz)
  • remove or reduce poss risk factor (edu on risks of recreational drugs)
  • increase poss protective factor (edu on vaccination)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Intervention studies are classified into what phases?

A

1– small trials with (2–100) healthy volunteers to assess safety and tolerability

2– efficacy and safety in larger groups of 100–300 people

3– provide definitive evidence of efficacy in those at risk, usually with RCT

4– routine use of an intervention to collect data on long-term efficacy and safety

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

why is an intervention study ideal for inferring causality?

A
  • exposure identified before outcome, so can establish temporarlity.
  • if the intervention reduces exposure, and thus the outcome is reduced, this establishes reversibility
  • subjects can be randomized, and if large enough sample, can help to equally distribute known and unknown confounders (no selection bias)
  • the intervention can be concealed, reducing information bias
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are some limitation to intervention studies?

A
  • not good for rare outcomes
  • selection bias, types of subjects that volunteer for study may not be generalizable to general public (external validity)
  • expensive
  • bias from types of pts loss to follow up (internal validity)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how do efficacy studies differ from effectiveness studies?

A

Efficacy studies– effect of intervention in experimental conditions, where max effort used to deliver intervention.

Effectiveness– real world conditions, where other obstacles may prevent the subjects from receiving the intervention.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are some ethical issues with intervention studies?

A
  • can’t withhold an intervention if it’s already available to the public, even though its benefits are not know (ex: screening OB US)
  • can’t withhold an intervention that’s already been shown in a previous study to be beneficial (HRT reducing CAD, subsequent studies didn’t support this)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what 2 criteria make up a RCT

A
  1. existence of a control arm

2. random allocation to intervention or control group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what are the options that a Control group can receive?

A
  • nothing
  • placebo
  • existing intervention
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are the 5 methods of allocation in increasing complexity order?

A
  • simple randomization
  • systematic randomization
  • blocked randomization
  • stratified randomization
  • matched pair randomization
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are the 5 methods of allocation in increasing complexity order?

A
  • simple randomization
  • systematic randomization
  • blocked randomization
  • stratified randomization
  • matched pair randomization
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

define– - simple randomization

A
  • simple randomization: shuffle labelled cards or computer generated random number list
  • systematic randomization
  • blocked randomization
  • stratified randomization
  • matched pair randomization
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

define– - systematic randomization

A
  • simple randomization
  • systematic randomization
  • blocked randomization
  • stratified randomization
  • matched pair randomization
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

define– - blocked randomization

A
  • simple randomization
  • systematic randomization
  • blocked randomization– ensures equal number in each arm, each block is a multiple of the gp number.
    ex– ABBA, BBAA, AABB
  • stratified randomization
  • matched pair randomization
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

define– - simple randomization

A
  • simple randomization: like flipping a coin, but may not result in equal # of subjects in each arm
  • systematic randomization
  • blocked randomization
  • stratified randomization
  • matched pair randomization
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

define– - systematic randomization

A
  • simple randomization
  • systematic randomization: subjects alternately placed in different arms, however pts on Monday may be inherently different than those on Tuesday
  • blocked randomization
  • stratified randomization
  • matched pair randomization
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

define– - blocked randomization

A
  • simple randomization
  • systematic randomization
  • blocked randomization: ensures equal #s in each arm, each block is a multiple of the grp #, like ABAB, BBAA, AABB, etc.
  • stratified randomization
  • matched pair randomization
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

define— stratified randomization

A
  • simple randomization
  • systematic randomization
  • blocked randomization
  • stratified randomization: divided into subgps by key risk factors, then equal #s into each arm using simple or block randomization (ex: stratifying infants into their villages, so effectiveness of vaccine is compared among infants of same village)
  • matched pair randomization
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

define— matched pair randomization

A
  • simple randomization
  • systematic randomization
  • blocked randomization
  • stratified randomization
  • matched pair randomization: a form of stratified randomization where individuals and communities are paired with another of similar baseline risk
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

how is the method “minimization” to allocate subjects to study arms different than the other forms?

A
  • it is not randomized
  • it’s goal is to allocate based on pre-specified criteria to get balanced arms
  • good for small studies
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is the difference between allocation concealment and blinding?

A

allocation concealment is only concealing the allocation process, to address selection bias.

blinding is concealing from all parties to avoid other forms of bias.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what are examples of more complex RCTs?

A

Cluster-randomized trials
Factorial design
Crossover design
Non-inferiority and equivalence designs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

when are Cluster-randomized trials used?

A
  • when the intervention is a on a community or cluster level, like measuring air pollution
  • when there’s a risk of “contamination” between control and intervention arms, like effect of educational leaflets
  • however, individuals in a cluster may share characteristics that can lead to confounding
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what is “factorial design”

A

allows for comparison of treatment A, tx B, tx A+B, and control. can save time and money.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

what is a crossover design?
best for what types of designs?
disadvantages?

A

each individual/ village acts as its own control. they’ll each be subjected to intervention and control, but in different orders. there’ll be a washout period.

best for interventions with short term effects.

usually longer than an RCT, so may have more drop outs.

31
Q

what is a non inferiority and equivalence design?

what is the purpose of this type of study?

A

to show that an intervention is as good or equal to an existing intervention.

  • helps to find a cheaper treatment
  • tx with less side effects
  • new method of delivery
32
Q

what situations warrant a non-randomized trial?

A
  • really complicated intervention studies
  • ethical reasons can’t RCT
  • evidence on a large scale is needed
33
Q

What is the intervention efficacy?

A

proportion of outcome that could be prevented by the intervention

formula= 1- relative risk

34
Q

what is intention to treat analysis?
What types of studies is it used for?

Does it tend to over or under estimate the effect?

A

Once randomized, always analyzed.

Subjects will be analyzed in the group they were allocated, regardless whether they finish the study or not.

Used in RCTs.

Tends to under estimate the effect.

35
Q

How is per-protocol different than intention to treat?

Does it tend to over or under estimate the effect?

A

only subjects who completed the study and adhered to the protocol are analyzed.

Tends to overestimate.

36
Q

ITT or per protocol more closely reflects real world circumstances?

A

intention to treat

37
Q

What is meta analysis?

A

Pooling individual results from several different studies.

38
Q

what is the goal of primary prevention

and what is an example?

A

to prevent or reduce exposure to a risk factor

ex: vaccination,
education around the risks of excessive etoh intake,
taxing tobacco,
banning public smoking

39
Q

what is the goal of secondary prevention

and what is an example?

A

early detection and treatment

ex: screening allows for early detection

40
Q

what is the goal of tertiary

and what is an example?

A

reduce severity and prevent complications by offering appropriate treatment and interventions

ex: preventing renal dz and glaucoma by maintaining good DM control

41
Q

what are the 2 main prevention approaches?

What type of risk calculation is being reduced?

A

1) individual/ high risk approach– used if the outcome is concentrated amongst high risk individuals
- reducing relative risk

2) population approach
- reducing absolute risk

42
Q

what are some limitations of the high risk approach?

A
  • stigmatizing to label someone high risk
  • puts guilt and burden on the high risk person while not recognizing the contribution of external forces
  • strategies may focus too much on the individual without addressing circumstances like poor nutrition or no access to clean water
43
Q

what is a benefit of the high risk approach

A

if resources or funds are limited, can focus on the group in a more concentrated way to get the most out of the intervention

44
Q

what is the prevention paradox?

A

a measure that brings large benefits to the community offers little to each participating individual

ex: most ppl wearing bike helmets will unlikely benefit from it bc head injuries are rare

45
Q

What formula/ calculation can help determine which approach is best (individual vs community)?

A

population attributable risk fraction

(incid outcome in pop - incid in unex)/ incid outcome in pop

46
Q

what are the 4 types of dose response curves?

give examples for each.

A

1) threshold- exposure that increases w/o adverse outcome until a threshold is reached, then adverse outcome increases rapidly.

Ex– intraocular pressure. So good to keep ppl under the pressure but further reduction doesn’t result in meaningful improvement.

2) linear- greater exposure, greater risk

ex– lung cancer and exposure to smoke, even 2nd hand smoke. best for efforts to be targeted at whole pop.

3) curve- outcome increases w/ exposure, but slope is shallow exposure small, but slope increases w/ more exposure.

ex– maternal age and down syndrome

4) J shaped– most complex, increased risk of outcome at both ends. “moderation is best”

ex– BMI

47
Q

what is the purpose of screening?

A

Promotes early detection and treatment.

Which is different from diagnosis, which confirms the outcome.

48
Q

what are the essential criteria for screening?

A
  • the availability of an effective and reliable screening method;
  • the availability of an intervention to reduce or improve outcome;
  • the safety and acceptability of the test to the individual; and
  • that the overall benefits of screening should outweigh any harm to the individual or population.
49
Q

what other considerations are there to know if screening campaign is feasible?

A
  • systems to identify and contact individuals
  • ensuring compliance (if test is invasive, pts may not want it, like colonoscopy)
  • availability of more extensive diagnosis (breast bx)
  • resources for increased treatment
50
Q

what are the ideal traits of a screening method?

A
  • inexpensive
  • comfortable for the pt
  • safe
  • easy
  • correctly identifies those at risk
  • evidence based
  • correctly identifies those with and without the condition
51
Q

how is the validity of a screening method and diagnostic test measured

A

sensitivity–proportion of those who have the outcome who are correctly identified (‘true positives’), correctly identifying those with dz

specificity–proportion of those who do not have the outcome who are correctly identified (‘true negatives’), correctly identifying those w/o dz

52
Q

what is the formula for sensitivity?

A

(# true +)/ (# w/ outcome) = A/ A+ C

53
Q

what is the formula for specificity?

A

(# true neg)/ (# w/o outcome) = D / B+ D

54
Q

what does a low sensitivity mean?

A

high false negatives

A / A+C

55
Q

what does a low specificity mean?

A

D/ B+D

high false positives

56
Q

what situations is a higher sensitivity preferred?

A

infectious disease. want low false negatives because they could continue spreading the infection if it’s not known.

57
Q

what situations is a higher specificity preferred?

A

want low false positives

  • if diagnostic test is expensive or invasive
  • if the diagnosis carries a stigma
58
Q

define– positive predictive value

A

likelihood of having the outcome based on the test result

or, chances of having the outcome when the test says I am positive

A/ A+B

59
Q

Define– negative predictive value

A

likelihood of not having the outcome based on the test result

or, chances of not having the outcome when the test is negative

D/ C+D

60
Q

What determines the predictive values?

A
  • sensitivity and specificity of screening method

- prevalence = (# w/ outcome)/ (tot # sampled)

61
Q

the higher the sensitivity will result in a lower/ higher negative predictive value?

A

higher NPV (because the false negatives are less)

62
Q

the higher the specificity will result in a lower/ higher positive predictive value?

A

higher PPV (because the false positives are less)

63
Q

if the prevalence decreases, this will increase or decrease the PPV and NPV

A

decreasing prevalence will decrease PPV and increase NPV

64
Q

what conditions would make it unethical to implement a screening program?

A

if there’s insufficient facilities or effective treatments for those who need them

65
Q

define– lead-time bias

what are the harms of lead-time bias?

A

when screening identifies an outcome earlier than it would otherwise have been identified, but has no effect on the outcome

increases the time in which a pt knows they have a disease, but doesn’t necessarily change the outcome. so may increase anxiety or exposure to ineffective treatment.

66
Q

define– selection bias

A

occurs because those who participate in screening programmes often differ from those who do not

67
Q

define– length-time bias

A

a form of selection bias and results from screening being more likely to detect outcomes with slow progression (longer asymptomatic or sub-clinical period) than rapid outcomes with a worse prognosis

For example, slower-growing breast cancer tumours are more likely to be detected by screening prior to the development of symptoms than rapidly growing tumours.

68
Q

define– over diagnosis

A

those diagnosed early with sub-clinical disease may have died of other causes before manifesting the outcome.

Through over-diagnosis, individuals may be needlessly turned into patients and exposed to treatments for an outcome that may have never become symptomatic, with associated negative psychological consequences related to such labelling. This may become an increasing problem with genetic screening for outcomes such as breast cancer.

69
Q

what is the best test/ trial to avoid bias in evaluating screening tests?

but why might this type of trial be inappropriate?

A

RCT would remove the bias via random allocation.

Might not be appropriate to evaluate screening test w/ RCTs bc:

  • if screening already available, can’t withold from subjects
  • those given a false-negative result from placebo-screening may be less likely to notice symptom development and might delay seeking treatment
  • observer bias– those responsible in pt care may know allocation and attribute sx to dz
  • differential misclassificaiton– contamination risk, those getting placebo may get screened elsewhere
  • large sample sizes needed to detect an effect
70
Q

• define strategies in terms of primary, secondary, and tertiary prevention

A

primary- reduces exposure
ex: vaccination, education programs

secondary- early detection and treatment
ex: screening programs

tertiary- prevent complications and progression of dz
ex: glucose control to prevent kidney dz or glaucoma

71
Q

• distinguish between population and high-risk targeting, and identify the most appropriate strategy for a given situation

A

population strategies- target whole population, best for reducing absolute risk.
ex: lowering obesity

high risk/ individual approach- best when burden is concentrated in a target group, especially if intervention is expensive or resource are limited.

72
Q

• list criteria for assessing the appropriateness of a screening programme

A
  • the availability of an effective and reliable screening method;
  • the availability of an intervention to reduce or improve outcome;
  • the safety and acceptability of the test to the individual; and
  • that the overall benefits of screening should outweigh any harm to the individual or population.
73
Q

• calculate measures of sensitivity, specificity, and predictive values of a screening method

A

sensitivity– true +. A/ A+C
specificity– true neg. D/ B+D
PPV– likelihood that a positive result will mean a positive dz A/ A+B
NPV– likelihood that a neg result will mean no dz. D/ C+D

PHM 101 Basic Epidemiology (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions