clinical trials

Question 1

case study or case series

Answer 1

no randomization
no comparison with untreated group
may provide info about side effects

Question 2

studies with a comparison (4 types)

Answer 2

1. historical controls
2. simultaneous non-randomized controls
3. randomization
4. stratified randomization

Question 3

historical controls

Answer 3

data used from comparison group from past
disadvantage: can be diff in base pop., disease rates, disease def, disease treamtnet, quality of data collected

Question 4

simultaneous non-randomized controls

Answer 4

can be a problem if assignment system can be predicted
EX: patients on even day are treament group, odd are controls
may lead to more admittance on even days

Question 5

intervention studies

Answer 5

test efficacy of preventive or therapeutic exposures
1. controlled clinical trials
2. community interventions

Question 6

controlled clinical trial characterisitcs

Answer 6

outcomes in treated compared with outcomes in control
both enrolled, treated, followed over same time period

Question 7

randomized controlled clinical trials characteristics

Answer 7

rigorous design, greatest control
randomized to intervention or control
double blind

Question 8

start with

clinical trials

Answer 8

study pop
then randomize
then see if they improve or don’t improve

Question 9

outcomes

clinical trials

Answer 9

endpoints
relative risk
hazard ratio
odds ratio from logistic regression

Question 10

clinical trials pros

clinical trials

Answer 10

no selection bias
certain exposure, must monitor
compliance
gold standard

Question 11

clinical trial cons

clinical trials

Answer 11

expensive
long
not generalizable
ethical issues

Question 12

selection of subjects

clinical trials

Answer 12

clear critera written in advance
can impact generalizability

Question 13

what does randomization help with?

clinical trials

Answer 13

decreases bias
establishes balance at baseline of confounders

Question 14

randomization issues

clinical trials

Answer 14

intervention group could have more loss to follow up (ITT)
if 1 or more arm is noncompliant, it will underestimate effectiveness

Question 15

goal of randomization

clinical trials

Answer 15

increase probability that there is an even distribution of observable and unobservable potential confounders between intervention and control

Question 16

single blind

Answer 16

subject unaware

Question 17

double blind

Answer 17

subject and experimenter doesn’t know group assignment

Question 18

why use a placebo

Answer 18

placebo effect exists: rates vary 0 to 35%
helps control unplanned crossover
even with placebo, many assume they are on the treatment

Question 19

non-compliance

Answer 19

patients agree to randomization, but don’t comply with treatment

Question 20

intentio to treat (ITT)

clinical trials

Answer 20

good bc intervention effect is diluted by crossover
if we don’t use ITT we violate randomization and introduce confounding

Question 21

variables of interest

clinical trials

Answer 21

cumulative incidence

Question 22

to measure degree of assoication

clinical trials

Answer 22

risk ratio
rate ratio

Question 23

special RCT

Answer 23

1. crossover
2. factorial design

Question 24

crossover RCT

Answer 24

patients may request crossover
crossover may be planned so subjects can be their own control

Question 25

factorial RCT

Answer 25

test 2 drugs or 2 nutrients
we can use same pop if:
1. outcomes are diff
2. mode of action are independent

Question 26

FDA required clinical trials for new meds

Answer 26

phase 1: clinical pharmacology for toxicolog and efficacy
phase 2: clinical investigations for efficacy and safety
phase 3: large scale RCT for effectiveness and safety
phase 4: post marketing surveillance

Question 27

clinical trials pros

clinical trials

Answer 27

best control over:
amount of exposure
timing and frequency of exposure
period of observation

randomization reduces likelihood that groups differ significantly

Question 28

clinical trials cons

clinical trials

Answer 28

artificial setting
limited scope of potential impact
adherence is difficult to enforce
ethical dilemmas

Question 29

community trials

Answer 29

determine benefit of new policy and programs
community is a defined unit

Question 30

community trials design

Answer 30

community randomized overtime
outcomes measured at baseline, then at follow-up

Question 31

community trials pros

Answer 31

only way to directly estimate change in behavior or modifiable exposure on incidence of disease

Question 32

community trials cons

Answer 32

inferior to clinical trials (worse control, monitoring, intervention delivery)
less options to randomize (decreased comparability)
affected by population dynamics, secular trends, nonintervention influences

Question 33

type I error

Answer 33

probability = alpha
we conclude treatments are different, but they really aren’t

Question 34

type II error

Answer 34

probability = beta
we conclude treatments aren’t different, but they are

Question 35

number needed to treat (NNT)

Answer 35

NNT = 1 / (mortality rate in untreated - mortality rate in treated)