Brainscape's Knowledge GenomeTM

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


See full index

Public Health > Lecture 11- Analytic Epidemiology > Flashcards

Lecture 11- Analytic Epidemiology Flashcards

1
Q

Descriptive epidemiology

A

Used when little is known about the disease, rely on preexisting data, who, where when, illustrates potential associations

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

Analytic epidemiology

A

Used when insight about various aspects of disease is available, rely on development of new data, why, evaluates causality of associations

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

Study designs of analytic epidemiology

A

Case control, cohort, prospective, retrospective

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

Case control study design

A

Study population divided into cases vs. controls

Cases and controls divided into exposed and unexposed

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

Odds ratio

A

Measure of association between exposure and outcome

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

If Odd ratio =1

A

Exposure does not affect odds of outcome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Odds ratio >1

A

Exposure associated with higher odds of outcome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Odds ratio <1

A

Exposure associated with lower odds of outcome

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

Where does a prospective cohort study start

A

With the unexposed and exposed group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Where does a retrospective cohort study start

A

With the disease and no disease of exposed and unexposed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Relative risk

A

Measure of the strength of association based on cohort studies and randomized clinical trials

=incidence in exposed/incidence in unexposed

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

Relative risk =1

A

Indicators no difference between groups

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Relative risk>1

A

Indicates risk among exposed group is higher

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

Relative risk <1

A

Indicates risk among exposed group is lower

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

When is relative risk used

A

When comparing outcomes of those who were exposed to something to those who are not exposed, calculated in cohort studies and randomized clinical trials, can’t be calculated in case control studies because the entire population at risk is not included or represented in the study

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

When to use odds ratio

A

Used most commonly in case-control studies, odds of exposure among cases is divided by odds of exposure among controls, provides a rough estimate of relative risk

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What do epidemiology study designs include

A

Experimental and clinical trials

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Experimental study design

A

Conditions are highly controlled- variables manipulated by researcher

Causality can be inferred by effects of influence of

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the measure of association in randomized clinical trials

A

Relative risk

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Cross over clinical trials

A

After the study progresses, the groups are switched, valuable when number of subjects is limited, potential confounders if the intervention has effects that carry over to the next portion

21
Q

Blind clinical trials

A

Blinding can reduce various types of bias

22
Q

Single blinded clinical trials

A

Subjects do not know which group they are in

23
Q

Double blinded clinical trials

A

Neither subjects or investigators know which groups the subjects are in

24
Q

Randomized clinical trials

A

Can maximize validity and minimize bias, subjects are recruited from a population and randomly allocated into groups, usually called study and control groups

25
Q

Community trial

A

Intervention designed for the usual purpose of educational and behavioral changes at the population level

Ex: water fluoridation in two communities in NY

26
Q

What does the 2x2 table compare

A

Your test to the best test that we have

27
Q

Sensitivity

A

% of truly positive identified by your test
= A(true positive)/ A +c(false negative)

28
Q

Specificity

A

% truly negative
=d(true negative)/d+b(false positive)

Example: a specificity of 95.6% indicates that only 4.4% of truly negative people would receive a false positive test

29
Q

Why is sensitivity vs specificity important

A

Determine whether its more important to rule a disease in or out, costs of being wrong

30
Q

What does high sensitivity mean

A

We are confident that the animal with a negative test does not have the condition

31
Q

What does high specificity mean

A

That we are confident that an animal with a positive test has the condition

32
Q

SnNOUT

A

Sn= sensitive
N= negative
OUT= rule out

33
Q

SpPIN

A

Sp= specific
P= positive
IN= rule in

34
Q

How to improve sensitivity

A

Parallel testing- running different tests simultaneously, disease positive if either or both test is positive, disease negative if both tests are negative, proves you not to have the disease

35
Q

How to improve specificity

A

Serial Testing- run screening test- then a confirmatory test if screening test is positive

Disease positive if confirmatory test is positive
Disease negative- if first test is negative
Proves you do have the disease

36
Q

Positive predictive value

A

Helps determine of the positive tests how many are truly positive

As prevalence decreases, PPV decreases too

True positive/ true positive +false negative

37
Q

Negative predictive value

A

Of my negative tests how many are truly negative

True negative/true negative +false positive

38
Q

Likelihood ratios

A

Includes the risk of the patient in front of us (pre test probability) and tells us how much that risk changes when he test is positive or negative (post test probability). Incorporates the probability that the test is positive in patients with and without the disease

39
Q

2x2 contingency table example: prevalence=10%, sensitivity=96% and specificity=98%. What is the positive predictive value

A

Prevalence=10% that means that (0.1x1000) 100 animals have the disease and (1000-100)=900 do not

Sensitivity=96% then (0.96x100)=96 (a- true positive) and c=(100-96)=4 (false negative)

Specificity=98%= (0.98x900)= 882 (d=true negative) and (900-882)=18 (b=false positive)

So PPV= a(true positive)/a+b(false positive)= 96/(96+18)=84%

40
Q

Equation for sensitivity

A

A(true positive)/a+c(false negative)

41
Q

Equation for specificity

A

D(true negative)/d+b (false positive)

42
Q

Equation for positive predictive value

A

A(true positive)/a+b(false positive)

43
Q

Equation for negative predictive value

A

D(true negative)/d+c(false negative)

44
Q

Calculating odds ration example: determine whether cats with hyperthyroidism and without hyperthyroidism differ in exposure to flame retardants

N=100,000
50 have hyperthyroidism

50 with hyperthyroidism, 38 of their owners indicated they have a couch treated with flame retardant

50 cats without hyperthyroidism 20,000 of the owners indicated they had owned a couch treated with flame retardant

A

38=A
20,000=B
C= 50-38= 12
D= (100,000-50)-20,000

OR=(A x D)/(B x C)= (38 x79,950)/ (20,000 x 12)= 12.7

Cats with hyperthyroidism were 12.7 times more likely to have exposure to flame retardants than cats without hyperthyroidism

45
Q

Calculating relative risk example: curious to see if the risk for developing FIP is different for cats belonging to smokers or non-smokers among a group of 500 kittens

A= 80
B= 120
C=15
D=285

A

RR- (A/(A+B))/ (C/C+D))
RR= (80/80+120)/ (15/15+285)

RR= 8.0
The risk of FIP is 8 times greater among cats belonging to smokers

46
Q

Example: you suspect hyperadrenocorticism in a 9yr, FS dog with 2 month history of increased appetite, increased thirst and urinary accidents. Which diagnostic test do you trust the most if he has a positive result

Urine cortisol creatinine ratio: sensitivity=90%, specificity=25%
ACTH stimulation: sensitivity=80%m specificity=85%
Low dose dexamethasone suppression: sensitivity=95%, specificity=50%

A

ACTH stimulation- most specific- fewer false positives

47
Q

Example: you serological test 140 wallabies for a disease, 35 wallabies test seropositive and 105 test seronegative. However, postmortem data reveals 5/35 of the seropositive wallabies are disease free and 4/105 of the seronegative wallabies are disease

What is the sensitivity of this serologic test:
A. 95%
B: 96%
C. 88%
D: 86%
E: 77%

A

Sensitivity= A/a+c= 30/(30+4)=88%

C. 88%

48
Q

example: you serologically test 140 wallabies for disease, 35 wallabies=seropositive, 105=seronegative, however postmortem data reveals 5/35 seropositive wallabies were disease free and 4/105 seronegative wallabies were diseased

What is the predictive negative value of this serologic test

A. 95%
B. 96%
C. 88%
D. 86%
E. 77%

A

NPV= d/(c+d)= 101/(4+101)=96%

B. 96%

49
Q

Example: you are using an FeLV test with sensitivity of 90% and specificity of 95%. Assuming the prevalence of FeLV in you area is 5% what is the positive predictive value of your test

A. 45%
B. 48%
C. 55%
D. 88%
E. 90%

A

PPV= a/(a+b)
Prevalence =5% so (0.05x1000)= 50 of 1000 animals have disease and 950 don’t

Sensitivity=90%= (0.90x50)= 45 (A)
C= 50-45= 5
Specificity=95% (0.95 x 950)= 902.5 (d)
B= (950-902.5)= 47.5

PPV= a/(a+b)= 45/(45+47.5)= 48%

Public Health (25 decks)

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