Unit 1-3

Question 1

What is epidemiology?

Answer 1

“the study of distribution and determinants of health-related states or events in specified populations and the applications of this study to control of health problems”

“study of frequency, distribution, determinants of health and disease in populations and application of this study to control health problems”

Question 2

Who is the father of nautical medicine?

Answer 2

Dr. James Lind

- randomized control trial to identify cure for scurvy

Question 3

Sir Percival Pott found the cause and effect link for…

Answer 3

occupational carcinogen

chimney sweepers cancer

Question 4

Horizontal vs Vertical transmission?

Answer 4

Horizontal = (members of same species) direct (person to person contact) or indirect (ingestion, aerial, latrogenic)
Vertical = mother to embryo, fetus, baby, just after pregnancy

Question 5

If a disease is transmitted from vertebrate animal to man what is this disease called?

Answer 5

Zoonotic disease

Question 6

Are vectors responsible for direct or indirect transmission?

Answer 6

indirect

especially zoonotic from original host/reservoir to second host

Question 7

What are the 4 stages of development of a disease?

Answer 7

1. Susceptibility
2. Pre-Symptomatic Disease
3. Stage of Clinical Disease
4. Disability or recovery

Question 8

From exposed to sufficient cause of disease and being able to detect disease state. What is this time called/

Answer 8

Latent period

Question 9

From exposed to sufficient cause of disease and onset of clinical signs. What is this time?

Answer 9

Incubation period

Question 10

Is bias and error the same or different?

Answer 10

different!
bias is systematic error.
There is a deisng flaw that affects validity

Question 11

What are 3 types of bias?

Answer 11

• selection bias
• information bias
• confounding bias

Question 12

What is the difference between the two causal pathways?

Answer 12

Direct causation: factor directly causes disease or health outcome without steps in between
Indirect causation: factor causes a disease but at least one intermediate step

Question 13

What are the 4 types of causal relationships?

Answer 13

necessary and sufficient
necessary but not sufficient
sufficient but not necessary
neither necessary not sufficient

Question 14

If there are 3 components to a sufficient cause what must happen for the disease/outcome to occur?

Answer 14

All three factor components in combination to constitute a sufficient cause

Question 15

Population Attribution Risk is defined as…

Answer 15

each sufficient cause responsible for a certain proportion of disease in the population

Question 16

What is selection bias?

Answer 16

the systematic difference between those participating and not participatin in study

Question 17

Loss to follow up is what type of bias?

Answer 17

Selection bias: participants in longitudinal study withdraw are systematically different than those who remain

Question 18

Healthy worker effect is what type of bias?

Answer 18

Selection bias:

i.e. people who participate are healthier than those who cannot participate

Question 19

What defines information bias?

Answer 19

data collected about an exposure or outcome that results in inaccurate or incorrect result

Question 20

Misclassification bias is what type of bias?

Answer 20

Information bias: assigning participants the wrong exposure and or outcome status

Question 21

What are two different types of misclassification bias and how are they different?

Answer 21

Nondifferential misclassification bias: all groups are equally likely to be accurately or inaccurately assessed or assigned
Differential misclassification bias: groups of participants are more likely than other groups

Question 22

What is confounding bias?

Answer 22

distortion in measure of association between exposure and health outcome caused by mixed effect of exposure of primary interest with extraneous risk factors

Question 23

What are 2 characteristics of confounding variable?

Answer 23

• factor X is a risk factor for disease B

- factor X is associated with factor A, but not a result of factor A

Question 24

What are 3 characteristics to consider when assessing given factor is a confounding variable?

Answer 24

• be associated with exposure
• be associated with outcome
• not be a result/cause d by the exposure

Question 25

How are 2 ways you can address confounding?

Answer 25

1. randomization

2. restriction/exculsion

Question 26

What can be used to determine health and disease outcomes and potential exposures?

Answer 26

tests!

these are assessment or decisions

Question 27

What are two categories of tests for health and disease outcomes?

Answer 27

• screening

- diagnostic

Question 28

What is the difference between high validity and high reliability?

Answer 28

• high validity = average of all test results are near true value
• high reliability = variation can be repeated numerous times or deviation from average result (high = narrow)

Question 29

What is validity?

Answer 29

how accurately a test measures on individual’s true biological value/overall infectionstatus or disease state

Question 30

When all diagnoses are correct with no misdiagnoses, what is this called?

Answer 30

Gold standard test.

Question 31

Sensitivity and Specificity measure what?

Answer 31

Test validity

Question 32

What is sensitivity?

Answer 32

ability of test to correctly identify those who have disease o or outcome of interest
- “true positive” = test positive (a) outcome positive (a+c)

Question 33

What is specificity?

Answer 33

ability of test to correctly identify those who do not have the disease of interest

Question 34

What is a test that is highly sensitive called?

Answer 34

Snout

high Sn

Question 35

What is a test that is highly specific called?

Answer 35

Spin

high Sp

Question 36

The observed proportion of disease within a population is defined as

Answer 36

apparent prevalence
(with new test)
(AP)

Question 37

The actual proportion of disease within population

Answer 37

true prevalence
(determined with gold standard reference)
(TP)

Question 38

What are predictive values used for?

Answer 38

demonstrate how useful a test result may be in a clinical setting or by health care provider

Question 39

What do PPV and NPV do?

Answer 39

PPV = true positive over all positive test results = a / (a+b)
NPV = proportion of true negatives over all negative test results = d / (c+d)

Question 40

What is the difference between series and parallel testing?

Answer 40

Series: use one test first, then the next

Parallel, multiple tests simultaneously

Question 41

What does it mean to have a reliable test?

Answer 41

Repeatability, ability of a test to produce similarly accurate results repeated over time

Question 42

What are 3 sources of variation that impact reliability?

Answer 42

• intrasubject
• intraobserver
• intERobserver (2 or more people disagreeing on interpretation of a test)

Question 43

What is the chance agreement?

Answer 43

2 individuals make the same assessment due to random chance rather than true agreement

Question 44

What is the kappa statistic?

Answer 44

measure of agreement beyond due to chance alone. multiple observers measure agreement between two tests

Question 45

What does series testing avoid?

Answer 45

prevents false positive. because you bring back positive for second confirmatory test

Question 46

What does parallel testing avoid?

Answer 46

prevents false negative. because you need both tests to be outcome negative to be outcome negative

Question 47

Series testing allows for ____ in net sensitivity and ____ in net specificity.

Answer 47

loss in sensitivity

gain in specificity

Question 48

The greater the kappa statistic, the ___ the agreement.

Answer 48

> 0.8 excellent agreement

<0.2 = slight agreement