CPPS 337 Flashcards
(157 cards)
Objective
Every experiment starts with a research question, which is stated as the study objective - the objective is whatever is going to be assessed or measured
- primary (efficacy of drug) and secondary objectives (safety of drug)
Example:
- Experiment: test new drug for migraine prophylaxis (prevention)
- Primary Objective: does drug A reduce frequency of migraines
Outcomes
specific assessments designed to help inform a study objective
(outcomes get you to objective - help you answer the research question)
1 or 2 primary outcomes that decide the success of your study
Examples:
- Change from baseline to week 24 in monthly migraine days (primary)
- Number of patients with a migraine 1 day after their dose
of Drug A
Enrollment
Patients that are recruited for study
- inclusion criteria
- exclusion criterai
Intervention group
Gets treatment
Control group
Does not get treatment
Randomization
Random allocation of participants to treatment and control group
Stratification factors
Want to keep t and c groups balanced for baseline characteristics - helps randomization be balanced
- Tell computer to make groups with equal number of moderate/severe asthma, and high/low dose corticosteroids
Allocation concealment
Concealing which group the patient has been allocated to
- make the allocation process automated and conducted by a third party
- can use interactive voice/web response system
Blinding
Matching control to treatment
- can use doubly dummy for different dosage forms: One group gets tablet and placebo shot, other gets placebo tablet and shot
Parallel control group
treatment and control groups observed at same time
Historical control group
control group taken from old study
Active treatment
active established drug thats given to control group
- active controlled vs plavebo controlled trials
Prospective study
looks forward - watches for outcomes like the development of a disease
- relates the outcome to suspected risk or protection factors
- clinical trials (testing new drug) always prospective - go forward in time
Retrospective study
looks backward - outcome established at the start of the study; examines past exposures to suspected risk or protection factors
- figuring out about AIDS: looked at patient history and found virus)
Historical control
the outcomes of the intervention group are compared to results from a comparable group of patients whose data is retrieved from a database from the past
Reasons to choose a historical control
- there is no active control
- use of placebo considered unethical (patients would suffer)
- intervention is so good that all patients should be given access
Reasons not to use historical control
- results depend on choice of control
- subject to bias
Crossover designs
all participants are exposed to all controls and interventions in the trial - patients serve as their own control - takes individual variability out of the eqn
- start on a and switch to b after a period of time
- assuming order does not matter
- washout period between switch so no lingering effects of one drug (hard to do cuz some effect may stay)
Withdrawal studies
participants on a particular treatment are taken off therapy or have their dosage reduced
- objective is to asses response to discontinuation or dose reduction
- evaluating duration of benefit of an intervention already known to be useful
- checking for rebound effect (making condition worse after discontinuation)
Cohort study
observing a group/cohort over time
- participants selected based on characteristic/exposure that may cause disease
- incidence of the disease in the exposed individuals is compared with the incidence in those not exposed
- example: Framingham study (tracking cardiovascular outcomes and risk factors for CV disease)
Cohort studies advantages
- can study multiple outcomes for a given exposure
- good for investigating rare exposures
- can calculate rates of disease in exposed and unexposed individuals over time
Cohort studies disadvantages
- Large numbers of subjects are required to study rare exposures
Prospective Cohort Studies
- Expensive
- Long
- Maintaining follow-up is difficult
- Loss to follow-up or withdrawals
Retrospective Cohort Studies
- Susceptible to selection bias
- Susceptible to recall bias
- Less control over what information is available
Case-control studies
compare patients with a disease/outcome of interest (case) with patients who dont have it (control)
- look back retrospectively to see how often a risk factor was present in each group to determine the relationship between risk factor and disease
Difference between case-control studies and cohort studies
Case-control studies identify subjects by outcome status at the outset of the investigation