Unit 05: Intervention Studies Flashcards
What is the basis of an intervention study?
- begin with a defined population in which participants are randomized to receive either a new treatment or the current treatment.
- follow the subjects in each group to see how many are improved in the new treatment group compared with how many are improved in the current treatment group.
- If the new treatment is associated with a better outcome, we would expect to find better outcomes in more of the new treatment group than the current treatment group.
What is a type of intervention study without comparison?
case study (aka case series)
What are Historical Controls used for?
- using a comparison group from the past for intervention studies.
- The data obtained from the study groups must be comparable in kind and quality (living conditions, lifestyles, etc.)
What are Simultaneous Nonrandomized Controls used for?
- assigning people into the control group by an assignment system (ex. assign patients by the day of the month on which the patient is admitted to the hospital.)
- the assignment system was predictable: it was possible for the physicians to know what the assignment of the next patient would be.
Is randomization a garantee of comparibility?
no
If randomization is done properly, we acheive…
non-predictability
What is the purpose of randomization? (2)
- prevent any potential biases
- increases the comparability (not garanteed)
What is Stratified Randomization?
- increases the likelihood of comparability of the study groups.
- stratify (stratum = layer) our study population by each variable that we consider important and then randomize participants to treatment groups within each stratum (randomize within each stratum).
What data must you collect on subjects when conducting an intervention study? (2)
- the treatment group and the treatment recieved.
- the overall outcome (criteria to distinguish outcomes muts have been established beforehand).
How is Masking (Blinding) used in intervention studies?
- when we would like the subjects not to know which group they are assigned to.
- through use of a placebo.
What is “double-blinding” in intervention studies?
The masking of both participants and study personnel (nobody knows who’s in what treatment group)
What is a Placebo?
an inert substance that looks, tastes, and smells like the active agent.
What are Lab experiments (randomized clinical trials)? What are some characteristics?
- highly-controlled environment, where potential confounders or other factors can be controlled and the frequency and dose of the challenge/exposure can be set.
- does not take into account a number of factors/exposures that are present in a real-world scenario.
- further studies (usually in the field) are required.
- evaluate one or more new treatments for a disease or condition.
- total control over the challenge/exposure and the environment.
TL;DR : look at disease in a controlled and clinical environment.
What are Field experiments (randomized field trials)? What are some characteristics?
- real-world setting.
- tend to be logistically more difficult to carry out than clinical trials, because these trials involve healthy rather than diseased people.
- require a greater number of subjects followed up for long periods of time.
- evaluate of whether an agent or procedure reduces the risk of naturally developing disease among those free from that condition at enrollment.
- little control over the challenge and the environment.
TL;DR : look at disease in a real-world scenario (i.e., the field).
Assume the following is your research question…
“Is a new, experimental treatment for HIV in adults more effective than the best currently available treatment for this population at preventing clinical disease progression?”
Write an example of a null and alternative hypothesis.
Null hypothesis: There is no difference between the experimental treatment and best currently available treatment in terms of ability to prevent clinical disease progression among adults with HIV.
Alternative hypothesis: The new, experimental treatment is more effective than the best currently available treatment at preventing clinical disease progression among adults with HIV.
must your testing methods be ethical? Do you reeeally need consent??? :0
duh.
(good job! that was a hard one!! :P)
Things that mst be considered when doing an intervention study.
(broad general topics. Use your imagination as to how they apply).
- outcomes
- ethics
- populations
- control groups
Whats a negative control?
- refers to a comparison group that does not receive an intervention.
- This approach is used when the research question is, “Is an intervention better than nothing?”
- This commonly involves the use of a placebo.
Whats a positive control?
- A positive control in a randomized trial refers to a comparison group that receives some alternate intervention.
- This approach is used when the research questions is, “Is a new intervention better than the old intervention?”
- This commonly involves the best currently available treatment.
What are control groups?
groups that allow for a proper comparison between treatments.
What’s a Complete randomized design?
All individuals are randomly assigned to the treatment or the control group.
Whats a Randomized block design?
Similar to stratified random sampling, where subjects are first grouped on the basis of factors of interest (e.g. age, gender, ethnicity, etc.)
Whats a Cross-over design?
Each subject spends time in the treatment and the control group (i.e., each subject, acts as its own control).
Whats a Factorial design?
Used when investigators want to assess two or more treatments.
What’s a randomized trial?
ensures that every subject has an equal chance to be in either the treatment or the control group.
As the size of the groups increases, treatment effect…
decreases (difference between groups decreases)
As the size of the groups increases, variation amonst individuals…
increases (difference within each group increases).
As the size of the groups increases, the number of covariates (other factors)…
increases
As the size of the groups increases, the number of groups…
increases
What is Wish bias?
This form of bias is introduced into a study by the tendency of patients or investigators to fit data or other information into a personal scheme of how they believe things ought to be.
What is Differential admission bias?
results when patients/subjects with certain characteristics are more likely to be admitted, or referred, to a hospital where a sample might be taken—resulting in a sample unrepresentative of the target population.
What is Recall bias?
relates to the ability of the study subject(s) to correctly remember information that occurred in the past.
What is Misclassification bias?
results from incorrectly classifying an individual.
What does a p-value of less than 0.05 represent?
the probability of the observed effect occurring due to random chance alone is less than 5%.
AKA statistical significance!!
randomized trials provide ____ evidence for a treatment or preventive action than observational studies, case studies, and expert opinion
stronger
For randomized trials with animal subjects, the guidelines are called…
REFLECT (Reporting guidelines for Randomized Controlled Trials for Livestock and food safety)
For randomized trials with human subjects, the guidelines are called…
CONSORT (Consolidated Standards of Reporting Trials)
