Public Health Flashcards
How to calculate positive predictive value?
True Positive / True Positive + False Positive
How to calculate negative predictive value
True negative / True negative + false negative
What is negative predictive value?
The proportion of people with a negative result who do not have the disease
What is positive predictive value?
The proportion of people with a positive test that actually have the disease
How to calculate sensitivity
True positive / True positive + False Negative
How to calculate specificity?
True negative / False positive + true negative
Give 3 strengths of cross-sectional studies
Quick/cheap
No long periods of follow up
Can be used for large data sets
Give 3 weaknesses of cross-sectional studies
Not suitable for rare diseases
Not suitable for diseases with a short duratiopn
Unable to measure incidence
Define sensitivity
The percentage of true positives. (The proportion of people who test positive among those who have the disease)
(sensitivity of 90% means 90% of people who have the disease will test positive)
Define specificity
Percentage of true negatives
(90% specificity = 90% of people who do not have the disease will test negative)
What are the 5 levels of Maslow’s Hierarchy of Needs?
Physiological needs.
Safety needs.
Love and belonging.
Esteem.
Self-actualisation.
Define Allostasis
The process of achieving stability, or homeostasis, through physiological or behavioural change.
Define Epidemiology
The study of the frequency, distribution and determinants of diseases and health-related states in populations in order to prevent and control disease
Define Incidence
The rate at which new diseases occur in a population in a certain time period
Define Prevalence
The proportion of a population found to have a disease at a point in time.
Define Person-Time
Describes the sum of the periods of time that each individual in the study has been at risk.
(in years/months or days) (i.e Person Years)
Used as the denominator in incidence rate calculations
Define relative risk. What does it tell us?
Describes the risk in one category relative to another.
I.e Ratio of risk of disease in the exposed vs the unexposed.
Tells us the strength of association between a risk factor and a disease.
What calculation can be used to work out relative risk?
Incidence in exposed ÷ Incidence in unexposed
Define attributable risk
Describes the rate of disease in the exposed that may be attributed to the exposure.
Tells us about the size of effect in absolute terms
How is attributable risk calculated?
Incidence in exposed - Incidence in unexposed
Define Bias
Describes a systemic deviation from the true estimation of the association between exposure and outcome
Name 2 types of bias
Selection Bias
Information Bias
What is selection bias
The people who choose to participate in screening programmes may be different from those who do not.
Proper randomisation is not achieved
What is information bias?
Information or measurement bias can be due to observer, participant or instrument error.
What is length-time bias?
Diseases with a longer period of presentation are more likely to be detected by screening than ones with a shorter time of presentation
What is lead-time bias?
Screening identifies diseases earlier and so gives the impression that survival is prolonged but in reality survival time is unchanged.
What is the Bradford Hill Criteria for Causation?
Consistency.
Biological plausibility.
Temporality - cause before disease.
Dose response.
Reversibility.
Strength of association.
Name 5 types of study
Ecological
Cross-Sectional
Case Control
Cohort
Randomised Control Trial
Which type of study uses routinely collected population level date to show trends and to generate hypotheses?
An Ecological Study
Which type of study looks at the population at a point in time?
A cross-sectional or prevalence study.
Which type of study compares people with a disease to those without a disease for age, sex, habits, class etc?
A case-control study. These are retrospective.
Which type of study follows a population over time to see if they’re exposed to the agent in question and if they develop the disease?
A cohort or incidence study. These are prospective.
What is a RCT?
Where a population is randomised to either an interventional or a control group. Often these are blind or double-blind trials.
Which type of study is also known as an incidence study?
A cohort study - follows a population over time to see if they’re exposed to the agent in question and if they develop the disease.
Which type of study is also known as a prevalence study?
A cross-sectional study. It looks at the population at point in time.
Define primary prevention.
Preventing a disease/condition from occurring in the first place. Eliminating RF’s that contribute to the disease.
Give an example of a primary prevention method.
Immunisations.
Define secondary prevention.
Detecting a disease as soon as possible in order to alter its course and to improve health outcomes.
Give 2 examples of secondary prevention.
Screening e.g. cervical smears, breast cancer mammograms.
Low dose aspirin/diet/exercise changes to prevent further heart attacks/stroke
Define tertiary prevention.
Trying to slow down disease progression, avoiding complications and helping people to manage their illness effectively.
Give 2 examples of tertiary prevention.
Diabetes management - diet advice, exercise programmes, self-monitoring, annual foot checks etc.
Stroke Rehabilitation
Give 4 different types of screening
Population based.
Opportunistic.
Screening for communicable diseases.
Pre-employment and occupational.
Define bioavailability
Refers to the fraction of administered drug that reaches systemic circulation (blood)
Give 3 causes of low bioavailability
First-pass metabolism (causes drug to be metabolised before adequate plasma concentrations are reached)
Insufficient time for absorption in the GI tract (if drug does not dissolve readily or cannot penetrate the epithelial membrane)
Pervious GI surgery (i.e bariatric surgery)
100 drug molecules are ingested. 90 survive the GI tract. 81 make it past the gut wall into the portal vein. Of the 81 that enter the liver, 41 make it into systemic circulation.
What is the bioavailability?
41/100 = 41%
