Epidemiology: Evidence Based Medicine

Question 1

Define: Epidemiology

Answer 1

The study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems

Question 2

An epidemiological research study compares two groups of animals, one group that all have the same, naturally occurring, disease, and another group that are similar in some ways (example: species, clients of same veterinary clinic) but none of the animals in this group have the disease of the first group. The researcher then compares the frequency of several potential exposure factors (example: diet, vaccination history, location of primary residence, exercise) between the two groups to look for patterns. This study is best classified as a:

Answer 2

Case-Control Study

Question 3

Which type of bias is best controlled with a good diagnostic test?

Answer 3

Misclassification Bias

Question 4

When reviewing research methods in effort to determine is a particular study may be helpful for your clinical decision making, what factor is most helpful to assess bias?

Answer 4

Random allocation of subjects to groups

Question 5

What is the difference between a cohort study and a case control study?

Answer 5

Classification: cohort study groups animals based on exposure status while a case control study groups animals based on disease status

Question 6

Which type of study allows for exploration of temporal cause and effect relationships?

Answer 6

Cohort study

Question 7

Which area of expertise is most important for veterinary practitioners to be able to evaluate the quality of information provided by scientific studies?

Answer 7

An understanding of the strengths and limitations of various study designs

Question 8

What study types provide the strongest evidence about clinically relevant questions?

Answer 8

Systematic reviews and meta-analyses

Question 9

When does selection bias exist?

Answer 9

When animals differ among study groups in more ways than just the intervention of putative risk factor assessed

Question 10

What is an example of selective bias?

Answer 10

Selection bias may occur when a veterinarian is more likely to administer the perceived best treatment to patients with the most severe clinical signs, which could result in an underestimation of the response to treatment because those patients would presumably be more difficult to treat than patients with less severe signs or in overestimation because those patients might show the greatest clinical response.

Question 11

When does information bias occur?

Answer 11

When certain animals or groups of animals are observed more closely, with different observation or monitoring methods, or for a longer period than other animals or groups of animals because of characteristics such as breed, age, housing, severity of clinical signs, or convenience

Question 12

What is an example of information bias?

Answer 12

Can easily occur when comparing the effects of a new intervention with those of a more traditional intervention because animals receiving the new intervention may be more closely observed than those receiving the more traditional (and thus previously evaluated) intervention.

Question 13

When does confounding occur?

Answer 13

when 2 factors are associated with each other but not evenly distributed among the subjects evaluated, making it difficult to identify which factor is truly associated with the outcome of interest

Question 14

Well-designed scientific studies involve what techniques for controlling bias?

Answer 14

Random selection of subjects that meet the study inclusion criteria, random allocation of subjects to treatment groups, and blinding of outcome assessors with regard to the treatment groups to which subjects were assigned

Question 15

Define: Systematic Reviews

Answer 15

Involve a rigorous and clearly defined process to provide summaries of previous studies on a specific topic and typically provide a more broad-based conclusion than for a single trial.

Question 16

Define: Randomized Control Trial

Answer 16

Experimental studies in which investigators assign subjects in an unbiased manner to receive the intervention or exposure being investigated or a control intervention (usually a placebo, sham treatment, or existing treatment).

Question 17

Define: Observational Studies
What studies fall under this category?

Answer 17

Cohort, case-control, cross-sectional
Investigators draw inferences about the effects of an intervention or putative risk factor in a clinically relevant, natural setting through observation of the subjects, without assigning them to receive particular interventions or undergo certain exposures.

Question 18

Strengths: Systematic Review / Meta-Analysis

Answer 18

Question 19

Limitations: Systematic Review / Meta Analysis

Answer 19

Question 20

Strengths: Randomized Controlled Trial

Answer 20

Question 21

Limitations: Randomized Controlled Trial

Answer 21

Question 22

Strengths: Retrospective/Prospective Cohort Study

Answer 22

Question 23

Limitations: Retrospective/Prospective Cohort Study

Answer 23

Question 24

Strengths: Case Control Study

Answer 24

Question 25

Limitations: Case Control Study

Answer 25

Question 26

Strengths: Cross-Sectional Study

Answer 26

Question 27

Limitations: Cross-Sectional Study

Answer 27

Question 28

Strength: Case Report/Case Series

Answer 28

Question 29

Limitations: Case Report/Case Series

Answer 29

Question 30

Define: Systematic Review/Meta-Analyses

Answer 30

Designed to answer a focused question, which leads to a systematic search of the literature with a critical review of the identified scientific studies in a transparent process that can be evaluated and repeated by others

Question 31

Define: Randomized Controlled Trials

Answer 31

Provides strong evidence that an intervention is
involved in the causation of or recovery from disease because the intervention can be shown to precede the outcome.

Question 32

Define: Cohort Study

Answer 32

Designed to evaluate the effect of a risk factor or intervention on an outcome of interest.

Question 33

Define: Case-Control Study

Answer 33

Subjects with and without the outcome of interest are identified and their history of exposure to specific factors is compared between the 2 groups.

Question 34

Define: Cross Sectional Studies

Answer 34

Typically require less time and fewer resources to complete than do other study types because they involve concurrent collection of data on putative risk factors or exposures and outcomes of interest.

Question 35

Define: Case Reports and Case Series

Answer 35

Essentially a description of a clinical experience or
series of similar clinical experiences involving ≥ 1 animal.
These types of studies are not controlled in that
they do not involve comparison of characteristics or intervention outcomes of case animals with those of control animals; only case animals are included in case reports and case series, and the findings are purely descriptive.

Question 36

Define: Confounding Bias

Answer 36

Confounding is a special type of bias by which a
factor other than the intervention or factor of interest is associated with the study outcome, but this factor is not distributed evenly among study groups.
Common examples of potential confounders include sex, breed, housing or environment, and age or body weight at the time of study initiation.