Unit 6-7

Question 1

A study that does not intervene or change anything in the person’s life is called….

Answer 1

observational study

Question 2

What type of study is an observational study?

Answer 2

analytical study

Question 3

What are 2 types of analytical studies?

Answer 3

observational and experimental

Question 4

What are 3 types of observational studies?

Answer 4

• cross-sectional
• case-control
• cohort

Question 5

What are 3 types of descriptive studies?

Answer 5

• case reports
• case series
• descriptive surveys

Question 6

What are the major differences between descriptive and analytical studies?

Answer 6

Descriptive:

• what?
• collects info
• does not establish association between cause and effect

Analytical:

• why?
• investigate the reason for disease/death/even to control the problem
• compares between groups
• association between E and O
• good for testing hypotheses

Question 7

When would an observational study be better than experimental study?

Answer 7

• intervention is unethical
• intervention is expensive
• exposure is complex/hard to control
• not practical to administer exposure

Question 8

How are cross sectional study subjects selected?

Answer 8

chosen without regard to exposure or outcome status

Question 9

How are case control study subjects selected?

Answer 9

chosen based on outcome status

Question 10

How are cohort study subjects selected?

Answer 10

chosen based on exposure status

Question 11

What are 5 main steps in cross-sectional studies?

Answer 11

• randomly sample from source population
• take measurements of individuals all at one point of time
• classify E+/E-
• classify O+/O-
• compare prevalence or odds of disease in E+ or E- groups

Question 12

What are some advantages of cross-sectional studies?

Answer 12

• can determine prevalence of E and O
• fast and inexpensive
• less bias than case control
• study permanent factors
• assess association between multiple E and multiple O
• random sampling, estimates all measures of association and effect but no true rates

Question 13

What are disadvantages of cross- sectional studies?

Answer 13

• not good for rare E or rare O (cuz random sampling)
• prone to major forms of bias if not considered (selection, information, confounding)
• measures prevalence, but not incidence (because it takes a snapshot of one moment in time)
• temporality (prevalence, not incidence, did E actually come before O?)

Question 14

What are 3 major steps for case-control studies?

Answer 14

• purposively sample individuals from population of interest O+ and O-
• classify each individual on basis of E+ or E-
• compare proportion of O+ subjects that are E+ vs E-

Question 15

What are some advantages of case-control studies?

Answer 15

• rare disease (outcome), not rare exposure
• to investigate source of an outbreak
• good for identifying multiple risk factors (E) for one disease (unknown cause)
• fast and inexpensive because retrospective (historical)

Question 16

What are disadvantages of case control studies?

Answer 16

• cannot calculate incidence or prevalence (chose on the basis of disease/not diseased
• examines only one outcome
• MOST prone to bias (looking back in time to obtain data)
• temporal relationship are issue in prevalent cases (new and old)
• control selection may be difficult to select

Question 17

What is a primary study base?

Answer 17

population which cases arise that can be easily defined
good sense of where population of all cases are coming from
(i.e. a daycare, a farm)
(for case control studies - selecting case population)

Question 18

What is a secondary study base?

Answer 18

population of potential study subjects that is one or more steps removed from primary study population
- wide range of backgrounds/difficult to define
(for case control studies - selecting case population)

Question 19

How are cohort study subjects selected?

Answer 19

on the basis of exposure status

Question 20

What do cohort studies measure?

Answer 20

incidence of disease (of new cases)

Question 21

What are advantages of cohort studies?

Answer 21

• good for RARE exposures
• several outcomes
• temporal sequence established (prospective)
• attain incidence data
• can measure all association and effect

Question 22

What are disadvantages of cohort studies?

Answer 22

• expensive
• time consuming
• bad for rare outcomes
• susceptible to loss to follow up

Question 23

What type of study cannot calculate relative risk?

Answer 23

• case-control studies

Question 24

What type of study can calculate all measures of association and effect?

Answer 24

cohort studies

• RR, OR, IRR
• RD, APe, PAR, PAF

Question 25

What are 2 types of experimental studies?

Answer 25

``` Lab experiments (clinical trials) Field experiments (field trials) ``` these are intervention based studies

Question 26

What are advantages of lab experiments/randomized clinical trials?

Answer 26

- highly controlled environment - confounding factors can be controlled - frequency and dose is set

Question 27

What are disadvantages of lab experiments/randomized clinical trials?

Answer 27

- does not take into account of other factors /exposures in real-world scenarios - further study required (field study)

Question 28

What is a "challenge trial"

Answer 28

- randomized clinical trial (lab experiments) | - study of subjects exposed to given exposure (i.e. a virus)

Question 29

What are advantages of field experiments/randomized field trials?

Answer 29

- real world setting | - assess impact of various treatments in setting that can be applied to future individuals

Question 30

What are disadvantages of field experiments/randomized field trials?

Answer 30

- logistically more difficult to carry out than clinical - involves healthy rather than diseased - may not develop disease o interest in short time frame - requires greater number of individuals to follow up for long time

Question 31

What is the main/major difference between clinical and field trials?

Answer 31

level of control clinical trials have total control over challenge/exposure and environment field trials aim to see if if agent/procedure reduces risk of naturally developing disease (therefore, little control)

Question 32

"Where the value of a treatment, old and new, is doubtful, there may be a higher moral obligation to test it critically than to continue to prescribe it year-in-year-out with the support merely of custom or wishful thinking" "The question at issue, then, is whether it is proper to withhold from any patient a treatment that might, perhaps, give him benefit. The value of the treatment is, clearly, not proven; if it were, there would be no need for a trial. But, on the other hand, there must be some basis for it – whether it be from evidence obtained in test tubes, animals, or even in a few patients. There must be some basis to justify a trial at all." These are definitions of ...

Answer 32

ethics

Question 33

A comparison group with no intervention in randomized trials is called...

Answer 33

Negative control

Question 34

A comparison group with an alternative intervention in randomized trials is called...

Answer 34

Positive control

Question 35

What are 3 ways to allocate individuals to treatment groups?

Answer 35

- complete randomized design - randomized block design (like stratified - grouped first by factors of interest i.e. age, ethnicity) - cross-over design (each subject spends some time in treatment, and some time in control)

Question 36

If a study subject is aware that they are receiving treatment for specific outcome and report improvements if they don't exist, this bias is called..

Answer 36

Wish bias | - tendency of patients or investigators to fit data of how they believe it should be

Question 37

When patients with certain characteristics are more likely to be admitted to hospital where their sample may be taken, this bias is called...

Answer 37

Differential admission bias | - the sample is unrepresentative of the target population

Question 38

The ability/inability of study subjects to correctly remember information that occurred in the past is what type of bias?

Answer 38

Recall bias

Question 39

Poor sensitivity or specificity of a test can lead to what type of bias?

Answer 39

Misclassification bias | - incorrectly classifying an individual

Question 40

Blinding is useful to eliminate what type of bias?

Answer 40

follow up bias

Question 41

What are 3 types of blinding?

Answer 41

- single blinding (subject OR researcher blinded) - double blinding (subject AND researcher) - triple blinding (subject, researcher, data analysts blinded)

Question 42

What are REFLECT and CONSORT?

Answer 42

guidelines for randomized trials to improve level of reporting?

Question 43

What does REFLECT stand for?

Answer 43

reporting guidelines for randomized controlled trials for livestock and food safety (animal subjects)

Question 44

What does consort stand for?

Answer 44

consolidated standards of reporting trials | human subjects