Lecture 15 9/23/24 Flashcards
What is the purpose of descriptive studies?
summarize clinical features and characteristics of a series of cases observed in clinical settings or in the population
What is the conceptual design of descriptive studies?
record and point out unique features and commonalities of a series of cases
What is measured in a descriptive study?
-frequency of diseases and a descriptive account of disease entity
-does NOT explain risk factors that may be associated with the illness or death
What are the strengths of descriptive studies?
-relatively inexpensive
-can be accomplished in a short time
What is the limitation of descriptive studies?
no associations can be made
What are the characteristics of a case report?
-detailed presentation of a single case
-generally not representative of the general course of disease
What are the characteristics of a case series?
-collection of cases
-useful in hypothesis generation
What is provided by a survey?
data about the frequency and distribution of a disease in a specified population
What is the purpose of a cohort study?
-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
What are the strengths of a cohort study?
-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
What are the limitations of a cohort study?
-inefficient for evaluation of rare outcomes
-can be extremely expensive and time consuming
-validity of results can be affected by losses to follow-up
What is the purpose of a cross-sectional study?
-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
What is the conceptual design of a cross-sectional study?
data relating to the disease status and risk factors that may be associated with disease are measured simultaneously
What is measured by a cross-sectional study?
-prevalence of infection/disease
-association between disease and risk factors
How is rate ratio of disease calculated?
prevalence of disease among exposed/prevalence of disease among non-exposed
How is rate ratio of exposure calculated?
prevalence of exposure among diseased/prevalence of exposure among non-diseased
What is an odds ratio?
-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
What are the strengths of a cross-sectional study?
-inexpensive and quick
-examine multiple associations for a single disease
What are the limitations of a cross-sectional study?
-difficult to establish temporal relationships between exposure and disease outcome
-cannot measure incidence or risk of disease directly
What is the purpose of a case-control study?
determine if some exposures in the past are likely to have been associated with the occurrence of clinical illnesses/deaths being observed
What is measured by a case-control study?
odds ratio; odds that a case was exposed/odds that a control was exposed
What are the strengths of a case-control study?
-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
What are the limitations of a case-control study?
-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
How do cohort studies compare to case-control studies and cross-sectional studies?
-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
