Clinical Trials

Question 1

experimental studies

Answer 1

investigator intervenes with the course of nature and assigns exposure (treatment) to subjects

Question 2

what is the goal of clinical trials

Answer 2

quantify the effect of an intervention

GOLD STANDARD for establishing causality because effect is relative to a comparison group

Question 3

control group

Answer 3

a comparison group to determine whether exposure to a factor caused the outcome

provides an estimate for disease occurrence had the factor under study not been present

Question 4

what is the goal of the control group

Answer 4

limit the differences between the treatment and control groups so that the only interfering cause of differences would be the assigned treatment

Question 5

inclusion and exclusion criteria

Answer 5

criteria by which subjects must meet in order to be enrolled

limits variability between groups but only PARTIALLY satisfies comparability

Question 6

randomization

Answer 6

avoiding differentiation assignment of treatment by randomly assigning

goal: equally distribute confounders between groups and reduce investigator bias

Question 7

does randomization always guarantee comparability between groups

Answer 7

NO - small sample sizes have a higher chance of confounders despite randomization

Question 8

what qualifies as a confounder

Answer 8

something that is causal to BOTH the exposure and the outcome

ex:
- disease: lung cancer
- exposure: smoking
- confounder: heart disease

subjects with heart disease should not be enrolled in a study of the effect of smoking on lung cancer because smoking also causes heart disease, so it is more likely that the heart disease subject has been a smoker

Question 9

confounding

Answer 9

mixing of effects; attributing an effect to one factor when in reality it is due to another

Question 10

what can help decreased confounding

Answer 10

large sample sizes - distributes confounders equally among groups

Question 11

masking/blinding

Answer 11

blinding the trial staff from knowing treatment status of subjects to ensure valid comparison

Question 12

single blind study

Answer 12

either the study subject or the investigator is unaware of treatment group

Question 13

double blind study

Answer 13

both the study subjects and the investigator are unaware of group allocation

Question 14

triple blind study

Answer 14

the study subject, investigator, and scientist analyzing the data are unaware of group allocation

Question 15

blocking

Answer 15

randomly chosen blocks used to assign treatments

ex. if block size is 4, then for every 4 subjects enrolled, 2 will be group A and 2 will be group B but by variable permutations

Question 16

blocking by time

Answer 16

the variable in enrollment is based on the TIME the patient was enrolled

ex. every week there will be 4 subjects enrolled - 2A and 2B so that if unexpected factors cause the study to end early, there will be equal numbers of As and Bs

Question 17

stratification

Answer 17

dividing the trial into many smaller trials in order to block on different risk factors (ex. breed, sex)

increases study efficiency by narrowing the confidence intervals

occurs BEFORE randomization

Question 18

multicenter trials

Answer 18

trials conducted in more than 1 location with the same protocol followed in each location

information gets processed by a single center

requires a very large sample size

Question 19

advantages of clinical trials

Answer 19

• best way to produce evidence for causal effect
• may be the only practical way to study certain clinical problems
• can sometimes be faster than observational studies

Question 20

disadvantages of clinical trials

Answer 20

• can be costly and time consuming
• not all projects can be experimentally studied
• may be ethical problems in doing the experiment
• outcome may be too rare to study
• narrower scope than observational studies