Types of Research Studies Flashcards
Questions to ask yourself when looking at a paper
- Does the paper have the right study design? Usually want randomized controlled clinical trial
2.Which level of evidence does the paper provide?
- Is the quality of the paper good enough to help me answer my particular question?
- Is the paper relevant to my clinical question, my population or patient?
Primary research studies
-case reports
-case series
-observational studies (cohort, case-control, cross-sectional)
-diagnostic test validity study
-experimental studies
-clinical trials
Secondary research
-Reviews (narrative, scoping, evidence based practice guidelines, systemic reviews, meta-analysis)
-economic analyses (partial budgets, decision analysis)
Case Report
-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
Case Series
-description of the presentation, diagnosis, treatment and outcome of a group of animals with the same disease
Limitations of a case series
- 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)
Surveys
-often involves obtaining a random sample from a population to get unbiased estimate of the variable of interest
>often prevalence of disease
Census
-a survey which involves all animals of the population
Limitation of surveys
-available study populations may not always be representative of true target population
Parameter vs statistic
Parameter: true value of characteristic being measured; from a census
Statistic: estimate of parameter; from a survey/sample
Observational Studies
-researcher studies a species of interest in its natural environment
Benefits to observational studies
- can examine a number og hypotheses that might be difficult to examine in experimental model
-can study rare events in large populations
Limitations to observational studies
-hard to control confounding variables (things in environment)
-harder to make causal associations
Goals of observational studies
- Measure disease frequency (prevalence/incidence)
- Assess distribution of disease (Who, Where, when?)
- Identify determinants of disease (risk factors)
**are exposure and disease linked?
Two directions to gather data
1.Prospective studies
- Retrospective studies
Prospective studies
-looking forward and getting new data after the start of a study
- clinical trials, experiments, cohort studies
Retrospective studies
- looking backward and using data that has already been collected
-case control studies
Types of observational studies
-cross-sectional study (longitudinal studies)
-case control study
-cohort studies
Cross-sectional studies
-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
Longitudinal studies
-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)
Disadvantages of cross-sectional studies
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
Cross sectional study categories
-Risk factor and disease
-Risk factor, no disease
-No risk factor, disease present
-no risk factor and no disease
Case-control studies
-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
Pros to case-control studies
-less expensive and time consuming
-efficient for studying rare diseases
