Epidemiology Flashcards
What is epidemiology?
The study of health and disease in populations
What is sensitivity?
If disease positive, the chance of being test positive
What is specificity?
If disease negative, the change of the test being negative
What is the predictive value of a positive test?
If tested positive, the chances of being disease positive
What is the predictive value of a negative test?
If tested negative for a disease, the chances of being negative
What is true prevalence?
Number of Disease positive
What is apparent prevalence?
Number of test positive
What is a cause? Usually multiple
Environmental or individual characteristics which affects the incidence of disease
What is a risk factor?
A variable whose presence or absence influences the incidence of a disease
Can be direct/indirect
What are associations?
Examining whether a variable is a risk factor, by examining the association between the variable and disease
What is the population at risk?
The number of individuals at risk from contracting a disease
Can be entire population
What is prevalence?
The number of individuals with a disease at a given time
What is incidence?
The number of new cases within a time period, as a proportion of those at risk
What is the equation for incidence rate?
Number of new cases/ population at risk
What is incidence risk?
The probability of an event occuring in a number of individuals followed for a period of time
What is relative risk/rate?
How many more times likely you are to contract a disease due to a risk factor
WHat is attributable risk/risk difference?
The risk of a disease in exposed individuals that can be associated with the risk factor
What is attributable rate difference?
The disease rate in exposed individuals that can be attributed to the risk factor
What is an endemic?
The constant presence of a disease (always there)
What is an epidemic?
A sharp increase of a disease above normal levels
What is an outbreak?
A sudden epidemic of short duration
What is a pandemic?
A worldwide epidemic
What is a confounding variable?
An outside influence that changes that outcome of an experiment
How do you deal with confounding variables?
Stratification
Matching
Attempting corrections
What is bias?
Something that makes non-random differences between groups being studied
What is population? What happens as this increases?
Total number of individuals
Becomes normal distribution
What is a sample? What is the problem with sampling?
A random selection of the population
Leads to uncertainty
What is a variable?
A characteristic that can be different in individuals
Can be categorical, quantities or ordinal (very ill, moderately ill, not ill)
What is used to calculate statistical signifcance?
Null hypothesis
Alternative hypothesis
Confidence limits
P value
What happens to specificity as sensitivity increases?
Decreases
What happens to the predictive value of a positive test as prevalence increases?
Also increases
When there is a low true prevalence, what happens to apparent prevalence?
Over estimation
What are the 3 types of epidemiological study?
Descriptive
Analytical
Experimental
What are the 4 types of analytic study?
CLCG Cross sectional Longitudinal Group based Case control
What is a cross sectional study? When is it not suitable?
Studying the prevalence of a condition and the possible risk factors
For low incidence/short duration
What is a longitudinal/cohort study and what are the advantages and disadvantages?
Follows a group for a period of time to see which individuals develop a disease
Expensive and time consuming
All individuals start healthy - informative
What is a case control study?
Looks at individuals with disease and compares with those without a disease (similar age, gender etc)
What is a group based study?
Comparing the experience of a population without examining characteristics
In general, what are analytical studies?
Examining the situation between characteristics, causes and outcomes of a disease
What is a descriptive epidemiological study?
Study which describes the situation of a disease in a population
What are experimental studies?
2 types
intervention studies put animals at subject to risk factor
clinical trials look for treatment
