Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
81 Cards in this Set
- Front
- Back
|
Randomized control trials
|
1. like a lab
2. investigator assigns exposure 3. it actually randomizes so that people are the same except for their exposure levels 4. great for handling confounding variables |
|
|
what are some of the major types of trials?
|
clinical, field and community intervention
|
|
|
What are examples of clinical trials?
|
1. subjects
2. studies outcomes |
|
|
what are some examples of field trials?
|
1. people from the community
2. studies SECONDARY prevention |
|
|
community intervention trials
|
1. applied to entire communities
2. can be smaller too |
|
|
others ways of classifying trials
|
purpose, randomization, treatment, # treatments
|
|
|
two types of treatment trials
|
preventative and therapeutic
|
|
|
preventative trials v. therapeutic
|
Preventative: prevent disease occurrence
Therapeutic: treating existing condition |
|
|
what are some examples of preventative trials?
|
agents, behavior modification...
|
|
|
what is a preventative trial and what is it used for?
|
a preventative trial is a trial that is used to prevent a disease that has already occurred. Some preventative trials include surgery or treatments. The preventative trials are usually compared to other known treatment plans.
|
|
|
what is a parallel trial?
|
in a parallel trial, each subject gets a treatment and then is followed up.
|
|
|
What is a crossover trial?
|
a subject can serve as his own control. Subjects are assigned both treatments
|
|
|
what is a simple design treatment?
|
each treatment group receives treatment with one SINGLE component
|
|
|
what is a factorial design?
|
each treatment group receives more than one treatment (you can test more than one agent)
|
|
|
Issues to consider when assessing a trial:
|
ethics, who to include, who to exclude
|
|
|
How do you know if your trial is ethical?
|
figure out who to include, why...
|
|
|
what is equipoise? (related to previous question on ethics)
|
a state of genuine uncertainty about the benefits or harms of two or more regimes
|
|
|
how do you decide who to include in a trial?
|
based on: geographic, demographic, medical, or temporal characteristics
|
|
|
who do you decide to EXCLUDE from a trial?
|
if it is unethical or not valid..
|
|
|
what are some examples of why you should exclude someone from a study?
|
1. harm
2. not effective 3. no compliance 4. no active participation |
|
|
examples of what to exclude from your study:
|
1. people who already had mumps
2. people who already had a stroke (studying blood medication) 3. alcohol addiction, mental problems... |
|
|
Why should we randomize?
|
1. to reduce confounding variables!!!!!
|
|
|
what does randomization accomplish?
|
if randomization works then the only thing that is different between your groups should be your exposure
|
|
|
how does Randomization work?
|
1. you can't have a predictable way of assigning people to groups.
AKA: it has to be random! 2. could be a random # generator 3. it works on an average so you want to have a large sample size so that more people get randomized |
|
|
Placebo/Sham Procedures
|
see next slide for definitions for each of these
|
|
|
Placebo
|
pharmacological inactive ingredient given as a substitute for an active ingredient (usually it looks very similar in shape, size, texture..)
|
|
|
sham procedure
|
fake procedure which is designed to resemble a legitimate procedure (should mimic the actual procedure being done)
|
|
|
what are some types of sham procedures?
|
drug trials: treatment that looks/smells/tastes just like the real thing
surgery trials: fake lifestyle: exercise? ok well make u stretch instead which actually isn't exercise which is why it is a sham procedure |
|
|
what is the placebo effect?
|
1. the psychological effect where a sham treatment produces a benefit
2. belief that having that drug is actually gonna have a benefit 3. you believe that you are going to have side effects |
|
|
what is blinding/masking?
|
this means that the investigator does not know whether the subject is getting a placebo or the actual drug. This can reduce potential bias.
- also helps prevent subjective outcomes. there are two types: double and single |
|
|
what is a single blinded experiment:
|
subjects don't know which intervention they are receiving
|
|
|
what is a double blinded experiment
|
when neither the investigator nor the subject knows what they are getting
|
|
|
What is assessment of compliance?
|
some people leave, somecome in, some take the pills some dont'.
drop ins: control group starts receiving the pills drop outs: people don't take all the pills |
|
|
noncompliance:
|
failure to follow the protocol to which assigned
|
|
|
what happens when you have poor compliance?
|
you have smaller effect sizes and more bias towards the null value
reduced statistical power |
|
|
what don't people comply?
|
1. they are confused
2. they forget 3. they don't like the side effects 4. they lose interest |
|
|
how do you improve compliance?
|
make it easier
enroll subjects who are willing to do this make it realistic blind people maintain contacts |
|
|
what are some reasons for stopping?
|
its harmful
treatment is less/more effective won't be able to answer |
|
|
what are the two types of bias?
|
information bias and volunteer bias
|
|
|
what is information bias?
|
SYSTEMATIC ERROR!!! (This means you don't measure something correctly...)
|
|
|
what is volunteer bias?
|
this is a type of selection bias...
those who volunteer are different than those who do not volnteer |
|
|
what are some other types of bias?
|
there is LOSS TO FOLLOW UP.
AND NON COMPLIANCE BIAS |
|
|
what are examples of information bias?
|
if exposure is not ACTUALLY randomized, there is likely to be bias.
also, if the investigators know about the assigning it is likely 2 be biased |
|
|
causality:
|
much easier to assess this in experimental vs. observational designs
|
|
|
what are the 2 views of case control studies?
|
1. the traditional view
2. the modern view |
|
|
what is the traditional view of case-control studies
|
1. like a cohort- you select diseased and non-diseased and then you compare exposure history
|
|
|
what is the modern view?
|
it is an efficient cohort study- NESTLED COHORT STUDY- good for determining exposure/disease outcomes
|
|
|
modern view example:
|
take a disease and then when searching for controls, just take all the people that DON'T have the disease and sample those people
|
|
|
when do you use case control?
|
when it is expensive and when the DISEASE is rare!!
when people are going in and out |
|
|
how do you select cases?
|
using birth or death certificates...
|
|
|
when would you use incident vs. prevalent?
|
incident: identifying cases
Limit: wait time prevalent: incident cases nt always available: limit: differences due to factors related 2 survival |
|
|
what are some types of controls
|
population, hospital, death, friends
|
|
|
when do you use population controls?
|
when the study is based on geographical location
limit: time consuming |
|
|
hospital/clinical controls
|
comes from hospitals but your control condition can't be related to your exposure of interest
|
|
|
special controls
|
friends, family...good: you know the people
limit: not always appropriate control doesn't always represent exposure distribution |
|
|
exposure information
|
face-to-face interviews, biomarkers can help
|
|
|
SELECTION BIAS:
|
happens when controls are not selected independently of exposure.
|
|
|
what are the types of information bias?
|
reporting
observer interviewer abstractor |
|
|
matching
|
make case and control similar on important predictors of disease
|
|
|
what are some strengths of a case-control study?
|
1. you can evaluate RARE outcomes
2. lots of exposures 3. not $ |
|
|
limits of a case control study
|
1. can't assess temporality
2. CAN'T CALCULATE INCIDENCE |
|
|
what is the difference between an observational study and an experimental study?
|
observational: exposures happen
experimental: investigator assigns |
|
|
when should you do a cohort?
|
rare exposures and when you want to evaluate multiple outcomes
|
|
|
what are the 2 types of cohort studies?
|
fixed and open
|
|
|
fixed cohort study:
|
defined amount of time
|
|
|
open or dynamic population:
|
can change over time
|
|
|
how 2 do a cohort study
|
id people at risk
define exposure of interest choose group follow them up |
|
|
special cohort
|
rare exposure
|
|
|
general cohort
|
common exposures based on specific shared characteristic
|
|
|
internal comparison group
|
selected from a population at the same time and place as exposure people
|
|
|
external comparison group
|
different place and time
|
|
|
population cohort
|
comparison group is usually the population
|
|
|
selection bias:
|
the way that people were enrolled in the study
|
|
|
information bias
|
basically, flaws in measurement
|
|
|
advantages
|
1. can assess temporality
2. you can assess risk 3. you can examine exposure 4. can look @ associations |
|
|
disadvantages of a cohort study:
|
1. you need lots of people
2. expensive, 3. long time things can change before the end of the study |
|
|
natural experiments
|
rare situations that are natural that mimic planned studies
|
|
|
nested case control studies
|
hybrid because it combines COHORT AND CASE CONTROL STUDIES
|
|
|
what is a nested case control study?
|
it is a case-control study that is within a cohort study
|
|
|
case crossover:
|
BRIEF EXPOSURE. there is a period of risk
advantages: no selection bias identical characteristics smaller sample sizes |
|
|
meta analysis
|
combine the results of multiple studies assessing association between exposure and disease
|
