Exam questions Flashcards
Definitions and exam-style questions (55 cards)
define prevalence
the number of affected persons present in the population divided by the number of people in the population.
explain the relationship between prevalence and incidence.
Prevalence is the number of existing cases within a population, whereas incidence is the number of new cases within a population.
define stillbirth rate
The number of stillbirths for every thousand live births in a country.
define life expectancy
the number of years a baby born today can be expected to live if it experienced the current age-specific mortality rates.
define healthy life expectancy
the number of expected years of life in good or fairly good general health.
define infant mortality rate
the number of dead infants (from age 0-1 years) that year against the number of live births that year.
define the PYLL index
potential years of life lost
the number of years of life lost when a person dies prematurely.
a measure of the relative impact of various diseases and lethal forces on society.
define the total period fertility rate
the average number of children that would be born to a woman over her lifetime.
what are the key design features of a cross-sectional study?
- Defining the study question
- Defining the target population
- Selecting the study population
- Collecting data
- Analysing data
- Interpreting results
what are the two main sources of bias in a cross-sectional study?
selection bias
information bias - recall bias
what are the key design features of a randomised controlled clinical trial?
PICO:
population
intervention
comparator
outcome
What are the two main sources of bias in a randomised controlled clinical trial? Give an example of each.
Performance bias
what are the key design features of a case-control study?
- decide sample size
- case selection
- control selection
- collect exposure data
- data analysis
- deal with validity threats
What are two of the main sources of bias in a case-control study? Give an example of each.
selection bias
information bias
What is matching in a case-control study and why is it used?
when variables between people are matched based on similar traits they have, to reduce the effect of confounding variables
write short notes on relative risk
Relative risk is the probability of an event occuring in the treatment group compared to the control group.
It can be calculated by
write short notes on population attributable risk
the proportion of the disease in the population that could be eliminated if exposure were eliminated.
expressed as a percentage of total risk in the population.
helps determining exposures relevant to public health in community.
reduction in risk is achieved if the population is entirely un-exposed.
write short notes on NNT
NNT= the number needed to treat
NNT is the number of patients you need to treat to prevent one additional bad outcome (death, stroke, etc.).
For example, if a drug has an NNT of 5, it means you have to treat 5 people with the drug to prevent one additional bad outcome.
write short notes on selection bias
Selection bias is when the initial cohort used in the study is not representative of the rest of the population,
write short notes on information bias
Information bias is when any systematic difference from the truth that arises in the collection, recall, recording and handling of information in a study, including how missing data is dealt with.
example = misclassification bias
what is the evidence pyramid for study designs?
Studies are assigned levels of evidence based on their methodology. The evidence pyramid is an easy way to visualize this hierarchy of evidence.
The top of the pyramid represents the strongest evidence.
At the base of the pyramid is unfiltered evidence including randomized controlled trials, cohort studies and case reports. These are individual reports and studies, also known as the primary literature.
what is the difference between necessary and sufficient cause?
Necessary cause has to be present for the disease to occur, for example, HIV has to be present for AIDS to occur.
A set of conditions is a sufficient cause when it always produces the outcome, for example, heavy smoking and lung cancer.
what is the epidemiological triangle?
the epidemiological triangle is used to determine the cause of infectious disease, non-infectious diseases and accidents or injuries.
It is made up of 3 parts:
- Host (intrinsic factors)
- Agent
-Environment (extrinsic factors)
Example when it is used - Tuberculosis
Host = poor nutrition, recurrent disease, low immunity
Agent = TB organism
Environment = crowding, poor ventilation, bad sanitation
what are Bradford Hill’s criteria of causation?
- strength of association
- consistency - replication
- specificity of the association
- temporal sequence
- biological gradient
- coherence
- experiment
- theoretical plausibility
- analogy
