Session 1: History of TB

Question 1

TB was initially thought of as what?

Answer 1

A genetic disease.

Question 2

What was thought to be a primary reason for TB decline over 20th century?

Answer 2

Improved standard of living

Question 3

TB properties.

Answer 3

Slow growing, airborne, not that easy to get (30% get infected, 5% get primary disease, 95% latent: of latent 5% reactivation, 95% persistent latent TB) Large % of those that get TB, don’t get sick.

Question 4

Latent TB state

Answer 4

Inhaled droplets of bacteria –> reach aveoli –> alveolar macrophages –> reaches lymph nodes –> bloodstream and disseminates –> controlled by cell mediated immune response

Question 5

Validity

Answer 5

lack of bias and confounding

Question 6

Bias

Answer 6

a “systemic error in the design or the conduct of the study that leads to erroneous association between exposure and disease:

Question 7

Confounding

Answer 7

“The mixing effects between an exposure, an outcome and a third extraneous variable “the confounder”

Question 8

Selection bias

Answer 8

error that results from the way you chose the study subject. Would happen different than if you chose randomly. What did an article say about who they said their source population was. That is generalizability.

Question 9

Generalizability

Answer 9

Generalization is a judgment in which the investigator relates the conclusions of a trial beyond the setting of the trial and the particular people studied in the trial

Question 10

What are common sources of selection bias

Answer 10

In case control-control studies: (control slection process, self-selection bias, differential surveillance, diagnosis of referral cases

In cohort studies: (deceased/moved (retrospective) and loss to follow-up (prospective).

Question 11

INFORMATION BIAS (SECOND KIND OF BIAS)

Answer 11

Has to do with how you access. (Measurement error “misclassification”, recall bias, Interview bias)

Question 12

Confounding

Answer 12

Distortion between the measure between exposure and outcome, and occurring when exposure is mixed together with another exposure (the confounder).

Question 13

Definition of a confounder

Answer 13

~Confounder is associated with the exposure AND the outcome
~Confounder is not on the causal pathway between exposure and outcome
~May be known or unknown

Question 14

Dealing with Confounding

Answer 14

Design Phase: Prevention (Randomization, restriction, matching)
Analysis Phase: Adjustment (Standardization, stratified analysis, multivariate analysis)

Question 15

Threats to validity

Answer 15

Right source population?
Did they get sample they wanted
correct data collection
look for association
look for confounding
did they conclude things logically

Question 16

Validity vs. generalizable

Answer 16

Are the results valid for the population that was [intended to be] studied? (Valid?)
Can the results be inferred to apply to some larger population? (Generalizable?)

Question 17

Factors supporting generalizability

Answer 17

Study results are valid
New populations are similar to the study source population
There are no other potential risk factors in the new population that were absent in the original population
Study and new populations are (relatively) contemporaneous

Question 18

What does validity refer to?

Answer 18

The internal consistency and and accuracy of a study

Question 19

In what instances is bias introduced?

Answer 19

the choice of the source population or selection from that population results in a systemic error related to the exposure or the outcome of interest.