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FAMILY, COMMUNITY AND PUBLIC HEALTH > EPIDEMIOLOGICAL STUDIES (079abcd) > Flashcards

EPIDEMIOLOGICAL STUDIES (079abcd) Flashcards

1
Q

What are the two main groups of epidemiological studies?

A

DESCRIPTIVE (no comparison group and ANALYTICAL (comparison group)

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2
Q

what research question format can we use for descriptive studies?

A

4Ws (who, what, where, when) . Cannot use PICO because there is no comparison group

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3
Q

What is the purpose of a descriptive study?

A

It is hypothesis GENERATING. Whether it is a case report, case series or ecological study, they all allow us to observe in order to generate a hypothesis or questions

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4
Q

What are the two main types of analytical studies?

A
  • Observational: no intervention, only comparison groups
  • Interventional.
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5
Q

what research question format can we use for analytical studies?

A

PICO, due to the presence of a comparison group/

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6
Q

What does PICO stand for?

A

P= Population
I= Intervention (or exposure for observational studies)
C= Control (the already existing gold standard drug for example)
O= Outcome

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7
Q

What is the purpose of an analytical study?

A

Hypothesis TESTING. Helps us test the hypothesis we come up with after certain observations made.

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7
Q

What is the purpose of an analytical study?

A

Hypothesis TESTING. Helps us test the hypothesis we come up with after certain observations made; are a certain exposure and a certain disease linked?

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8
Q

What are the 3 descriptive studies?

A

Case report ( describes a clinical phenomenon in a SINGLE patient)
Case series ( similar to case report but for more than one patient)
Ecological studies (data collected on GROUPS)

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9
Q

What are the disadvantages of case report/ case series?

A

They lack generalizability
prone to potentially unmeasured confounding.

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10
Q

What does an ecological study describe?

A

It shows correlations between average exposures in various populations and overall frequency of disease in these populations. It collects data on

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11
Q

How do we test the hypothesis that we generate from descriptive studies?

A

do an analytical study (include comparison groups)

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12
Q

benefits of an ecological study?

A

data easy to obtain
- study time is short
- helpful in forming quick opinions

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13
Q

what is the ecological fallacy?

A

when you make conclusions about INDIVUALS using ONLY analysis of GROUP data.
Fallacy: common errors in reasoning that will undermine the logic of your argument

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14
Q

What are the 3 main observational analytical studies?

A

Cohort, Cross sectional, Case control

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15
Q

what is a cross sectional study

A

measures exposures and disease status at one point in time ( takes a snapshot of the population), therefore it simultaneously evaluates exposure and outcome in a population.

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16
Q

what is the only study we use to calculate prevalence?

A

Cross sectional

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17
Q

difference between prevalence and incidence?

A

Prevalence: how many people in the population have the disease/ total population at a certain point in time
Incidence: the measure of how many new cases a disease arise in a certain time period

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18
Q

advantages of a cross sectional study?

A
  • helps us calculate prevalence of chronic diseases
  • simple, inexpensive, doesn’t need to much time
  • helps us determine the severity of an epidemic
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19
Q

disadvantages of a cross sectional study?

A
  • not an appropriate study to measure prevalence of short lived or acute conditions (since people get cured quickly)
  • cannot guarantee temporal relationship, so wrong conclusions could e made about risk factors of disease
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20
Q

What is a cohort study?

A

A study that starts of with disease free people, of whom are exposed to the risk factor of interest and whom are not exposed, and follows them with time to see if there is a difference in incidence of the disease in one of the two groups to see if the risk factor either increases, decreases or does not affect your risk of disease.

21
Q

what are the types of cohort study?

A

prospective ( start date is TODAY and follows through with the study participants to see what happens)
retrospective (get disease free people from past medical records and see where they are today)
reconstructive ( combines retrospective and prospective. start with disease free people from past medical records and carry through with the study)

22
Q

what measures of association can we get from a cohort study?

A

Incidence, relative risk, attributable risk (check notes for formulas)

23
Q

what is confounding?

A

A situation where a measure of association between a certain exposure and outcome is distorted by the presence of another variable.

24
Q

what is a very common confounder?

A

age and sex

25
Q

how do we deal with confounding?

A

either in the design stage or stage of analysis.
in the design stage:
- admission of those only free from the confounder in the study (restriction)
- randomization to distribute confounders equally
- equally distributing the confounders in all study groups
in the analysis stage:

26
Q

advantages of cohort study?

A
  • can ensure a temporal relationship
  • can study many outcomes from a single exposure simultaneously
  • suitable for rare exposures
  • free from recall bias
27
Q

disadvantages of cohort study?

A
  • takes a long time
  • needs a large number of people
  • not suitable for rare diseases
  • expensive
  • ethical problems
  • people may change their behaviors during the study (smoking for example)
  • loss of some indivuals during follow up
28
Q

What is a case control study

A

A study design in which induvials with a condition of interest (cases) are compared to people w/o the disease (controls) are regard to one or more exposures.

29
Q

which study is usually done as the first approach to test causal hypothesis?

A

case control, because it is relatively easy and inexpensive

30
Q

when is a case control study preferred to all of the other study designs?

A
  • rare diseases
  • when little is known about risk factors and we want to test multiple exposures at once
  • dynamic study population
31
Q

how many control groups should we have in a case control study for every case?

A

we should have at least one control group for every case, an extra control group would add statistical power to the study (however 3 groups is too much)

32
Q

what is the measure of the strength of the association between exposure and outcome used in a case control study?

A

odds ratio

33
Q

what may be some problems faced when trying to measure exposure in a case control study?

A

Recall bias: cases will remember their degree of an exposure more than the control if they think that exposure is what caused the disease
Interviewer bias: interviewer will ask about exposure more thoroughly in a case

34
Q

when should we use odds ratio instead of relative risk?

A

when prevalence of the disease in the general population is low and the risk ratio is low. if the disease prevalence is high, odds ratio overestimates the relative risk/

35
Q

advantages of a case control study?

A
  • quick and inexpensive
  • can test multiple exposures at once
  • suitable for rare diseases
    -minimal ethical problems
  • no loss of follow up (attrition problems)
36
Q

disadvantages of case control?

A
  • recall bias
  • selection of control group is difficult
  • odds ratio is an estimate of the RR only with diseases of low prevalence.
  • cannot confirm temporal relationship
37
Q

sources of bias in case control?

A
  • selection bias: difficult to get appropriate controls, same may turn out to be misdiagnosed/ undiagnosed
  • recall bias
  • reporting bias: lies about the answer
38
Q

What is a clinical trial?

A

A prospective interventional analytical study, comparing the effect of an intervention against a placebo or an already existing gold standard treatment.

39
Q

How do we carry out the clinical trial?

A

Select your population at risk. Use a sampling technique to get your study group, then split into an intervention group and a placebo group (this step may be randomized in an (RCT). Allow for some time for the drug to have an effect and then look at the outcomes and analyze it

40
Q

what are the two types of study designs we took for clinical trials?

A
  1. one armed clinical trial
  2. cross over design
41
Q

describe how the first clinical study design you mentioned is done.

A

ONE ARMED CLINICAL TRIAL: The simplest of clinical trials. you simply just give the drug in question to your sample and observe after time to see if there was an outcome or not (doesn’t compare it to a placebo or different drug, just done to see if it works or not)

42
Q

describe how the second clinical study design you mentioned is done.

A

CROSS OVER DESIGN:
Study population is selected, and split into an intervention group and a placebo group (this step could be randomized) and wait for some time to check for outcome. Any resuls are recorded, and then participants wait what is called a “washout period” where they make sure that they stop taking the drugs they previously took so any effect that drug had wears off. After the washout period, the two groups switch the drugs they were taking and then after some time, they check the outcome and compare.

43
Q

what is randomization?

A

the process where the study participants are assigned to the intervention or placebo group by a random process such as neither the investigator nor the patient decide what they will take.
every participant has an EQUAL CHANCE to receive either the intervention or the control treatment.

44
Q

what is blinding?

A

masking induvial participating in the trial from the treatment assigned

45
Q

what are the two most important methods to remove bias in a clinical trial?

A

randomization and blinding

46
Q

what are the RCT endpoints?

A
  • primary endpoint ( cure or achievement of goal)
  • surrogate endpoint (biomarker intended to substitute for a clinical endpoint)
    -composite endpoint ( where the intervention is considered a success or a failure with any of many listed outcomes)
  • safety outcomes ( rate of adverse events)
47
Q

what is the helsinki declaration?

A

A formal code of ethics for physicians who engage in clinical research. investigators planning to do clinical trials should consult these documents for ethical considerations.

48
Q

how are events monitored during the RCT?

A

-Interim analyses (analysis of data at regular intervals)
-Data and safety monitoring board: determines if the continuation of the study is appropriate, scientifically and ethically/

49
Q

how are the results from the RCT analyzed?

A

Intent to treat analysis: involves all participants that enrolled in the trial regardless of whether they completed the study or not
per protocol analysis: includes only the people who completed the trial
- relative risk, attributable risk reduction, number needed to treat, efficacy (RRR)

FAMILY, COMMUNITY AND PUBLIC HEALTH (10 decks)

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