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POTH RESEARCH > lect 4: case control > Flashcards

lect 4: case control Flashcards

1
Q

is case control in observational or experimental

A

observation

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2
Q

which is better at determining “causality” (cannot actually determine causality, but better at telling you the relationship between two variables): Cross sectional or case control

A

case control

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3
Q

what are the differences between observational and experimental

A

observational: does not intervene (the intervention/exposure/risk factor and the randomization of the study subjects are NOT manipulated by the reseachers), cannot determine causality,

experimental: intervenes (the intervention/exposure/risk factor and the randomization of the study subjects are manipulated by the reseachers), can determine causality,

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4
Q

true or false: alllllll observational study designs cannot determine causality

A

false, cohort can infer causality

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5
Q

which of the 3 observational study designs, which provides the least evidence for causality and which provides the most

A

least (cross sectional)
most (cohort)

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6
Q

does case control provide evidence of causality and explain

A

no, it can identify assocaition between exposure and the outcome but we might not be 100% sure of the temporal factor (if the exposure truly occurred before the outcomes)

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7
Q

are crosss sectional designs done at 1 point in time or across time

A

one point in time

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8
Q

are case control designs done at 1 point in time or across time

A

1 point in time

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9
Q

what is the general purpose of the case control study

A

study of causal factors (identify risk factors)
=links one variable/factor to another where one is though to be the cause of the other

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10
Q

in a case control study, which comes first exposure or outcome

A

exposure precedes outcome

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11
Q

true or false: in case control exposure precedes outcome

A

true

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12
Q

explain the general design of case control

A

you have a study of “persons with the disease of interest/CASE” and a suitable control group of persons without the disease/control
=choosing populations based on the outcome

looking retrospectively to compare how the two groups differ in their exposure level to the risk factor

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13
Q

true or false: in a Case study design = outcome is not known and looking back to collect data to look at frequency of exposure and compare the control and case group

A

false, the outcome is known

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14
Q

using smoking and lung cancer, explain how you would conduct a case control study

A

outcome of interest = lung cancer
exposure/risk factor of interest= smoking

case = people who have lung cancer
control= people who do not have lung cancer

look back retrospectively to see the exposure level to smoking that the case and control groups had to determine the assocation between level of exposure to smoking and the development of lung cancer

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15
Q

be able to explain/draw a 2x2 case control table (know what a, b,c,d means)

A
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16
Q

in case control, is data collected in one point in time or over time

A

one point in time (contrast to cohort where you measure the effect over time)

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17
Q

explain who is the case in case control study design

A

those with the outcome/condition/event

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18
Q

those with the outcome/condition/event
case or control

A

case

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19
Q

explain who is the control in case control study design

A

those without the outcome./condition/event

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20
Q

those without the outcome./condition/event

case or control group

A

control

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21
Q

what type of bias is common in case control and why

A

sampling/selection (because you are not randomizing the people in the design)

information bias (recall)

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22
Q

since sampling/selection bias is common in case control study, what is a way to minimize that bias

A

matching

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23
Q

explain matching in case control studies

A

Matching is defined as making cases and controls equivalent with respect to factors other than the exposure or factor being investigated
Cases and controls need to be similar on all other variables except the exposure and the outcome
(age sex, place of residence, time of hospitalization)

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24
Q

to control for confounding variables incase control study, what do we do

A

matching

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25
Q

what is the general definition of odds ration

A

measure of association
OR describes the odds (i.e., the degree to which) the presence of one condition is associated with another condition
E.g., The degree to which having diabetes is associated with carpal tunnel syndrome

Odds Ratio of exposure
The odds of exposure in those with the outcome (cases) compared to the odds of exposure in those without the outcome (controls)

26
Q

ODDs ration explnation and formula

A

Odds Ratio of exposure
The odds of exposure in those with the outcome (cases) compared to the odds of exposure in those without the outcome (controls)

OR = odds of exposure in cases (a/c) / odds of exposure in controls (b/d)

27
Q

odds ratio is equivalent to what in this calss

A

relative risk

28
Q

what is the relationship between CI and OR

A

The OR is accompanied by a confidence interval (CI), which provides a range of values within which the true OR is likely to fall
(look to CI to know if the value from the OR is signifciatnf or not)

29
Q

in a 2x2 table, outcome (disease status) is the general column or row

A

column

30
Q

in a 2x2 table, exposure status is the general column or row

A

row

31
Q

in a 2x2 table, what does cell A mean

A

disease is present and exposure is present

32
Q

in a 2x2 table, what does cell c mean

A

disease is present but no exposure

33
Q

in a 2x2 table, what does cell b mean

A

no disease present but have exposure

34
Q

in a 2x2 table, what does cell d mean

A

no disease present, no exposure

35
Q

in a case control study, cells A and C represent to controls or the cases

A

cases

36
Q

in a case control study, cells B and D represent to controls or the cases

A

controls

37
Q

odds of exposure in cases is what letters

A

a/c

38
Q

odds of exposure in controls is what letters

A

b/d

39
Q

be ablle to construct a 2x2 table when the exposure is not binary

A
40
Q

if OR is greater than 1 and 95% CI does not include 1, what does that mean

A

exposure significant increases the odds of the outcome/disease

41
Q

if OR is greater less 1 and 95% CI does not include 1, what does that mean

A

then the exposure significant decreases the odds of the outcome/disease (protective)

42
Q

if OR is = 1 and 95% CI does not include 1, what does that mean

A

then exposure does not affect the odds of an outcome

43
Q

what would the OR and CI look like if exposure does not affect the odds of an outcome

A

OR =1
CI does not include 1

44
Q

what would OR and CI look like if the exposure significant decreases the odds of the outcome/disease (protective)

A

OR less than 1 and CI does not include 1

45
Q

what would OR and CI look like if exposure significantly increases the odds of the outcome/disease

A

OR greater than 1 and 95% C1 does not include 1

46
Q

in OR, the null value (value that determines significance) is 1 or 0

A

1 (odds of outcome are the same in both control and cases)

47
Q

in RCT, the null value (value that determines significance) is 1 or 0

A

0 (difference between means)

48
Q

a 95% CI that includes 1 means no statistical significance or statistical significance

A

none

49
Q

larger CI = low or high presencion of the OR

A

low level of precision

50
Q

narrow CI = low or high presencion of the OR

A

higher precision of the OR

51
Q

in the assocaition between home hazards and falls, interpret the OR 9.25 (CI: 1.22-70.07

A

Interpretation: Children with access to high furniture had 9.25 times the odds of falling compared to children without access to high furniture.
=since CI does not include one the finding it statistically significant
=there is a low precision since large CI

52
Q

in the assocaition between cell phone use and cancer, interpret an OR 1.32 (CI=0.98-1.97)

A

The findings of this study indicate that people who use cell phones have 1.32 times higher odds of having cancer compared to people who don’t use cell phones. However, the findings are not statistically significant as the confidence interval includes 1. (CI is narrow so good precision of the OR)

Interpretation 2: The findings of this study indicate that those who use cell phones have 32% higher odds of developing cancer compared to people who don’t use cell phones. However, the findings are not statistically significant as the confidence interval includes 1

53
Q

in the assocaition between exercise and intracranial aneurism, interpret an OR 0.60 (CI=0.30-0.90)

A

Interpretation 1: The study’s findings indicate that people who exercise have 0.60 times the odds of having an intracranial aneurism compared to people who don’t exercise. The results are statistically significant as the confidence interval does not include 1. High precision because narrow CI

Interpretation 2: The findings of this study indicate that people who exercise have 40% lower odds of having an intracranial aneurism compared to people who don’t exercise. The results are statistically significant as the confidence interval does not include 1.

54
Q

what are the strengths of case control studies

A

Good to study rare conditions
Good to study conditions where it would be unethical to expose the participant (ie: do not have to manipulate the exposure)
Falls hazard, smoking etc

55
Q

what are the weaknesses of case control studies

A

unclear temporal relationship b/w exposure and disease (hard to know which comes first)

information bias (recall bias)
=ascertainement of past exposures can be difficult

selection bias (use matching)

56
Q

true or false: case control studies are prospective studies and explain

A

false, they are retrospective because they start from the outcome and look back in time to see the exposure

57
Q

in case control studies, the sample is based on the outcome or the exposure

A

the outcome

58
Q

in a case control study, is the outcome dichotomous/binary

A

yes because there are only 2 possibilities (case/control, disease/no disease)

59
Q

OR is a measure of association: true or false

A

true

60
Q
A

POTH RESEARCH (7 decks)

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