Types of Research Studies

Question 1

Questions to ask yourself when looking at a paper

Answer 1

1. Does the paper have the right study design? Usually want randomized controlled clinical trial

2.Which level of evidence does the paper provide?

3. Is the quality of the paper good enough to help me answer my particular question?
4. Is the paper relevant to my clinical question, my population or patient?

Question 2

Primary research studies

Answer 2

-case reports
-case series
-observational studies (cohort, case-control, cross-sectional)
-diagnostic test validity study
-experimental studies
-clinical trials

Question 3

Secondary research

Answer 3

-Reviews (narrative, scoping, evidence based practice guidelines, systemic reviews, meta-analysis)

-economic analyses (partial budgets, decision analysis)

Question 4

Case Report

Answer 4

-descriptive report of unique or interesting case (A story)
>identify new or unique disease
>cannot make conclusions regarding efficacy of treatment
>often an opinion of how to handle case

Question 5

Case Series

Answer 5

-description of the presentation, diagnosis, treatment and outcome of a group of animals with the same disease

Question 6

Limitations of a case series

Answer 6

• no disease free animals for comparison

-any differences in treatment or management have not been allocated (may be due to owners preferences or vet decisions)

Question 7

Surveys

Answer 7

-often involves obtaining a random sample from a population to get unbiased estimate of the variable of interest
>often prevalence of disease

Question 8

Census

Answer 8

-a survey which involves all animals of the population

Question 9

Limitation of surveys

Answer 9

-available study populations may not always be representative of true target population

Question 10

Parameter vs statistic

Answer 10

Parameter: true value of characteristic being measured; from a census

Statistic: estimate of parameter; from a survey/sample

Question 11

Observational Studies

Answer 11

-researcher studies a species of interest in its natural environment

Question 12

Benefits to observational studies

Answer 12

• can examine a number og hypotheses that might be difficult to examine in experimental model

-can study rare events in large populations

Question 13

Limitations to observational studies

Answer 13

-hard to control confounding variables (things in environment)

-harder to make causal associations

Question 14

Goals of observational studies

Answer 14

1. Measure disease frequency (prevalence/incidence)
2. Assess distribution of disease (Who, Where, when?)
3. Identify determinants of disease (risk factors)
   **are exposure and disease linked?

Question 15

Two directions to gather data

Answer 15

1.Prospective studies

2. Retrospective studies

Question 16

Prospective studies

Answer 16

-looking forward and getting new data after the start of a study

• clinical trials, experiments, cohort studies

Question 17

Retrospective studies

Answer 17

• looking backward and using data that has already been collected

-case control studies

Question 18

Types of observational studies

Answer 18

-cross-sectional study (longitudinal studies)
-case control study
-cohort studies

Question 19

Cross-sectional studies

Answer 19

-sample population is selected randomly or sometimes by convenience with no prior knowledge about exposure or disease status

-sample examined at one point in time

-each sampling unit is assessed for the factor of interest and outcome of interest during a snapshot in time

Question 20

Longitudinal studies

Answer 20

-a cross-sectional study that follows the sample population over time to assess for various outcomes

**allows for incidence to be calculated (which does not occur in cross-sectional studies)

Question 21

Disadvantages of cross-sectional studies

Answer 21

WEAKEST OBSERVATIONAL DESIGN

-difficult to determine temporal sequence of exposure and effect
-usually dont know when disease occurred
-rare events are difficult to examine
-quickly emerging diseases are difficult to study

Question 22

Cross sectional study categories

Answer 22

-Risk factor and disease
-Risk factor, no disease
-No risk factor, disease present
-no risk factor and no disease

Question 23

Case-control studies

Answer 23

-separate samples of animals/herds with and without the outcome of interest who are assessed for exposure to factor of interest

-good for rare or acute cases
-easy to perform but prone to bias
-retrospective in nature

Question 24

Pros to case-control studies

Answer 24

-less expensive and time consuming
-efficient for studying rare diseases

Question 25

Cons to case-control studies

Answer 25

-inappropriate when disease outcome for a specific exposure is not known at start of study

• exposure measurements taken after disease occurrence

-disease status can influence selection of subjects

Question 26

Bias in case control studies

Answer 26

• bias in selection of cases

-bias in selection of controls

Question 27

4 strategies for control selection

Answer 27

-hospital/clinic based controls
-matching
-population based sample of cases
-two or more control groups

Question 28

Measurement bias

Answer 28

-retrospective nature of ID of exposure to risk factors
>recall bias
>individual recalling data recorded prior to outcome occurring

**need to use blinding- observers and study subjects don’t know the case-control status and the risk factors being studied

Question 29

Cohort studies

Answer 29

-two samples of subjects (one with exposure, one without exposure), and followed through time for a predetermined period to determine outcome
-collected prospectively

**best observational design

Question 30

Cohort study strengths

Answer 30

-exposure status determined before disease detection
-subjects selected ahead of disease
-able to study multiple outcomes for each exposure

Question 31

Cohort study limitations

Answer 31

-expensive
-time consuming
-inefficient for rare diseases or diseases with long latency
-loss of followup can be a major problem

Question 32

Experimental studies

Answer 32

-study performed on an animal in controlled and artificial surrounding
>disease often artificially created or induced
>lab species can be used as a model
>usually comparing two or more interventions

Question 33

Clinical trials

Answer 33

-interventions given to groups of patients and followed up to see what happens
-treatments randomly allocated
-patients not kept in controlled environment

Question 34

Randomized controlled clinical trials

Answer 34

-experimental subjects compared against other subjects who receive either a placebo or standard treatment
>random avoids bias

Question 35

Advantages of clinical trials

Answer 35

-allows for specific hypothesis to examine a patient group
-easier to control confounding variables and avoid bias
-more likely to determine causality
-can be conducted in natural environment with field trial
-allows for meta-analysis later

Question 36

Disadvantages of clinical trials

Answer 36

-expensive
-time consuming
-difficult to do on rare diseases/events
-controlled by large pharmaceutical companies
-can introduce hidden bias

Question 37

Narrative reviews

Answer 37

-review literature and give advice
-often covers a subset of studies based on availability or author selection =selection bias

Question 38

Scoping Reviews

Answer 38

-used to describe available literature on a often broad topic
>includes charting and mapping
>describes volume and nature of literature available

Question 39

Systemic reviews

Answer 39

-standardized and rigorous methodologies to review scientific literature for a PICO
>minimizes bias
>very comprehensive (includes all literature including grey literature)
>identifies, appraise, synthesize all studies

Question 40

Grey literature

Answer 40

-documents produced on all levels of government, academics, business, and industry
>ex. conference abstracts, unpublished trial data, reports, policies, government publications

Question 41

Meta-analysis

Answer 41

-applying statistics to a systemic review of all clinical trial data
>quantitative summary; combined measure of treatment effect
>can be used to estimate relative importance of different factors affecting the outcome of interest