Disease Occurance And Study Designs Flashcards

1
Q

What is the target population of a study?

A

Population to which we want to generalize our results

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2
Q

What is the source population of a study?

A

Population from which subjects were drawn

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3
Q

What is the study population?

A

Group actually studies

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4
Q

What type of measure of disease occurrence, is the number of animals that have the disease (or other condition of interest) ?

A

Count

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5
Q

What type of measure of disease occurrence is the count of animals with the disease as a fraction of the total?

A

Proportion (Prevalence)

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6
Q

What type of measure of disease occurrence is the number of diseased animals compared to healthy individuals ?

A

Ratio

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7
Q

What type of measure of disease occurrence is the frequency a disease occurs in a population over the time?

A

Rates (eg incidence)

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8
Q

What is point prevalence? What type of study usually determines this?

A

Proportion of animals disease at any point in time

Cross-sectional study

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9
Q

What is period prevalence ?

A

Proportion of the study population that is diseased during a specific period of time

=(#cases/period of time) / (total population/period of time)

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10
Q

What is incidence? What kind of studies do we use this in

A

The number of new cases of disease that occurs in the population over time

Prospective studies -> clinical trials/prospective cohort

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11
Q

What is a cumulative incidence?

A

Proportion of disease-free individuals that become diseased in a specified period of time

= (#new cases / time) / (total population/time)

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12
Q

What is a specific type of cumulative incidence used in outbreak and is usually applied to a narrowly defined population?

A

Attack rate

= (#new cases/time) / (#exposed/time)

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13
Q

What type of rate can be used when animals enter and leave a study population? How is it calculated?

A

Incidence rate

= (#new cases/time) / (sum of length of time that each animal is at risk)

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14
Q

T/F: prevalence is dependent on incidence and duration of disease

A

True

-> the longer old cases survive, the higher the prevalence

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15
Q

What is the best measure to access overall burden of disease?

A

Prevalence

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16
Q

What is the best measure to access increase or decrease in frequency of disease?

A

Incidence

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17
Q

What is mortality rate??

A

=(#deaths/time) / (total population/time)

18
Q

What is case fatality rate?

A

= (#cases dead) / (total diseased)

19
Q

What is cause-specific mortality rate?

A

= (#deaths from dz/time) / (total population/time)

20
Q

What type of study does not compare groups and only has a single case?

A

Case report

21
Q

What type of study does not compare groups, but has a few cases in the study?

A

Case series

22
Q

What type of study does not compare groups, but has many individuals in the study?

A

Cross-sectional descriptive

23
Q

What type of study compares groups and exposes the animals to a exposure/treatment?

A

Clinical trial

24
Q

What type of study observes groups that are selected based on population?

A

Ecological study

25
Q

What type of study compares group by selecting individuals to represent a population?

A

Cross-sectional analytical

26
Q

What type of study observes individuals that are chosen to represent outcomes ?

A

Case control

27
Q

What type of study observes individuals that are chosen to represent an exposure?

A

Cohort (prospective or retrospective)

28
Q

T/F: cross-sectional descriptive studies can be used to estimate the amount and distribution of disease, usually with prevalence

A

True

29
Q

What are the advantages of a descriptive cross-sectional study?

A

Can generalize to a population
Fast and cheap
Good descriptive baseline data

30
Q

If an exposure is associated with an outcome, it is called a ________________

A

Determinant/risk factor

31
Q

Allocation of subjects to a treatment group only occurs in experimental studies. How should allocation be done?

A

Randomized -> study effect of treatment with no other factors

32
Q

T/F:Radom sampling is representative of a population and each subject has an equal chance of selection?

A

True

33
Q

Non-randomized sampling may not be representative of a population. What are two ways these subjects may be sampled?

A

Purposive eg. Every 4th dog spayed is sampled

Convenience eg. Animals seen at vet clinics

34
Q

What are advantages of experimental studies?

A

May establish causality
Well controlled -> free of bias and confounding
Statistically very powerful
Exposure and outcome are clearly measured (no recall bias)

35
Q

What are disadvantages associated with ecological studies?

A

Ecological fallacy-> relationship at population level may not hold true at individual level

Cannot detect complicated relationships

36
Q

A cross-sectional analytical studies selects individuals based on? What is measured?

A

Selected to represented population, regardless of outcome or exposure

Both exposure and outcome is measured

37
Q

A case control study selects individuals based on? What is measured?

A

Outcome (group with dz and control)

Measure exposure between two groups

38
Q

T/F: controls in a case-control study must come from the same population as the diseased individuals

A

True

39
Q

In cohort studies, individuals are selected based on? What is measured?

A

Exposure status

Measure outcome

  • prospective -> incidence of dz
  • retrospective -> prevalence
40
Q

What type of study is better and establishing causality, retrospective cohort or prospective cohort studies?

A

Prospective