You have seen combinations of case-control design with cohort design earlier...recall:
- Case-cohort
- Selection of cases and a sub-cohort from the source, or original, cohort - i.e., you identify the cases from the existing cohort and select a smaller set of the cohort to follow over time as a comparison to the cases
- Nested case-control
- Within a cohort study, cases and controls are selected for a smaller case-control investigation, for example, determining case status and collecting blood or tissue samples among the cases and selected controls in a cohort; genotyping (exposure status) is done using the samples for these subjects, not the entire cohort; the association between disease and the genetic factor is assessed)
Once again, recall the comparative advantages and disadvantages of case-control and cohort studies:
Cohort
- Calculates incidence rate, risk, and relative risk
- Potentially more strong for causal investigations
- Expensive
- Long-term study
- Need large sample size
- Good for rare exposure
- Good for multiple outcomes
- Less potential for recall bias
- More potential for loss-to-followup
- Possibly generalizable
- Allows examination of natural course of disease, survival
Case-Control
- Only an estimate of relative risk
- Potentially less strong for causal investigation
- Inexpensive
- Short-term study
- Powerful with small sample of cases
- Good for rare disease
- Good for multiple exposures
- More potential for recall bias
- Less potential for loss-to-followup
- Probably not generalizable
- Does not allow examination of natural course of disease, survival