Lecture 15 9/23/24

Question 1

What is the purpose of descriptive studies?

Answer 1

summarize clinical features and characteristics of a series of cases observed in clinical settings or in the population

Question 2

What is the conceptual design of descriptive studies?

Answer 2

record and point out unique features and commonalities of a series of cases

Question 3

What is measured in a descriptive study?

Answer 3

-frequency of diseases and a descriptive account of disease entity
-does NOT explain risk factors that may be associated with the illness or death

Question 4

What are the strengths of descriptive studies?

Answer 4

-relatively inexpensive
-can be accomplished in a short time

Question 5

What is the limitation of descriptive studies?

Answer 5

no associations can be made

Question 6

What are the characteristics of a case report?

Answer 6

-detailed presentation of a single case
-generally not representative of the general course of disease

Question 7

What are the characteristics of a case series?

Answer 7

-collection of cases
-useful in hypothesis generation

Question 8

What is provided by a survey?

Answer 8

data about the frequency and distribution of a disease in a specified population

Question 9

What is the purpose of a cohort study?

Answer 9

-to determine incidence rate; rate at which healthy subjects in a given population become sick
-to determine risk rate/ratio; probability of a subject developing a disease following an exposure to risk factors

Question 10

What are the strengths of a cohort study?

Answer 10

-can examine multiple effects of a single exposure
-can clarify temporal relationship between exposure and disease
-allows direct measurement of incidence of disease in the exposed vs. non-exposed groups
-ideal for evaluation of rare exposures

Question 11

What are the limitations of a cohort study?

Answer 11

-inefficient for evaluation of rare outcomes
-can be extremely expensive and time consuming
-validity of results can be affected by losses to follow-up

Question 12

What is the purpose of a cross-sectional study?

Answer 12

-estimate the prevalence of an infection/disease in a population at a point in time or given time period
-make association between set of risk factors and prevalence of infection/disease

Question 13

What is the conceptual design of a cross-sectional study?

Answer 13

data relating to the disease status and risk factors that may be associated with disease are measured simultaneously

Question 14

What is measured by a cross-sectional study?

Answer 14

-prevalence of infection/disease
-association between disease and risk factors

Question 15

How is rate ratio of disease calculated?

Answer 15

prevalence of disease among exposed/prevalence of disease among non-exposed

Question 16

How is rate ratio of exposure calculated?

Answer 16

prevalence of exposure among diseased/prevalence of exposure among non-diseased

Question 17

What is an odds ratio?

Answer 17

-ratio of two odds
-odds of disease among exposed/odds of disease among non-exposed
-odds of exposure among diseased/odds of exposure among non-diseased
-can be calculated as AxD/BxC

Question 18

What are the strengths of a cross-sectional study?

Answer 18

-inexpensive and quick
-examine multiple associations for a single disease

Question 19

What are the limitations of a cross-sectional study?

Answer 19

-difficult to establish temporal relationships between exposure and disease outcome
-cannot measure incidence or risk of disease directly

Question 20

What is the purpose of a case-control study?

Answer 20

determine if some exposures in the past are likely to have been associated with the occurrence of clinical illnesses/deaths being observed

Question 21

What is measured by a case-control study?

Answer 21

odds ratio; odds that a case was exposed/odds that a control was exposed

Question 22

What are the strengths of a case-control study?

Answer 22

-quick and inexpensive
-suited for eval. of diseases with long latent periods
-optimal for eval. or rare diseases
-can examine multiple etiologic factors for a single disease

Question 23

What are the limitations of a case-control study?

Answer 23

-difficult to directly compute incidence rates of disease in exposed and non-exposed individuals
-temporal relationship between exposure and disease may be difficult to establish
-particularly prone to bias

Question 24

How do cohort studies compare to case-control studies and cross-sectional studies?

Answer 24

-cohort studies begin by looking at exposures and following for the outcomes
-case-control studies start with outcomes and determine potential exposures retroactively
-cross-sectional studies look at exposures and outcomes simultaneously