Study Designs Flashcards
List the six types of study designs
- Cross- sectional
- Case- control
- Prospective cohort
- Retrospective cohort
- Case series
- Case report
Define cross- sectional study (and provide an example)
• Is an observational study
• Used to describe what is happening at the present moment
* “Burden of disease”
• The outcome and exposures are measured simultaneously
• Measures prevalence of the outcome
Collecting a group of people/smokers and seeing how many of them have oral cancer
Define case control study (and provide an example)
- Compares a group with the outcome (cases) with a group without the outcome (controls)
- Eligibility criteria for cases and controls -controls: people must be similar in most aspects except the outcome of interest/disease
Having a group of people with oral cancer and a group without oral cancer, then seeing how many of them are smokers
Define prospective cohort study (and provide an example)
- Starts with a group of healthy participants relative to the outcome of interest
- Participants are classified according to exposure status: an exposure group and non- exposure group
- A follow up is used to assess the outcome
Having a group of all non- smokers with no oral cancer, then exposing a portion of them and seeing how many of the exposed (and unexposed) get the outcome
Define retrospective cohort study (and provide an example)
- Study subjects based on their exposure status
- Both exposure and outcome have already happened in past
- Compare the group with the exposure with a group without the exposure
Define case series and case reports
Case series
• Describes a group of patients with a similar symptoms or outcome/ undergoing similar treatment
• No control group
Case report • Like a case series, but on a single patient • A descriptive study • Describes a single patient • An event that has happened or observed
Explain the advantages of a cross- sectional study
- Easy to perform, doesn’t take too many resources
- No follow up
- Ideal for prevalence studies
- Used as a basis for further research
Explain the disadvantages of a cross- sectional study
- Difficult to determine whether the outcome preceded exposure or whether the exposure resulted in the outcome
- Weak evidence of cause and effect
Explain the advantages of a case- control study
- Multiple exposures can be assessed for a single outcome
- Easy, quick and cheap
- Used to investigate rare diseases
Explain the disadvantages of a cross- sectional study
- Difficult to determine whether the outcome preceded exposure or whether the exposure resulted in the outcome
- Weak evidence of cause and effect
- People may not be truthful about having the outcome: recall bias
Explain the advantages of a prospective cohort study
- Multiple outcomes can be assessed
- Start before the outcome occurs, so you know that the exposure is probably the cause of the outcome
- Strong cause and effect evidence
- Ideal for estimating incidence
Explain the disadvantages of a prospective cohort study
- Time, effort, resources are needed
- If you start with 100 patients, you may not end the study with 100 patients: drop-out bias
- Multiple outcomes can be assessed
Explain the advantages of a retrospective cohort study
- Data comes from medical records: reliable information
- Easy and less time consuming
- Rely on already collected data
Explain the disadvantages of a retrospective cohort study
• Must rely that on others for accurate recordkeeping
Explain the advantages of a case series
Help to develop hypotheses, create case definitions, study clinical symptoms and signs, understand the natural history
