Public Health Flashcards
What is Prevalence?
The number of existing cases at a particular point in time (can be expressed as a percentage or per e.g. 100,000)
What is the stages of change model?
Not thinking (pre contemplation) –> Thinking about changing (contemplation) –> Preparing to change –> Action –> Maintenance –> Stable/Changed Lifestyle or Relapse
What is Primary prevention?
The aim of primary prevention is to prevent a disease becoming established. It aims to reduce or eliminate exposures and behaviours that are known to increase an individuals risk of developing a disease
What is Secondary Prevention?
The aim of secondary prevention is to detect early disease and slow down or halt the progress of the disease
What is Tertiary prevention?
Once Disease is established, detectable and symptomatic, tertiary prevention aims to reduce the complications or severity of disease by offering appropriate treatments or interventions
Lifestyle changes to prevent CHD?
SNAP
Smoking
Nutrition
Alcohol
Physical activity
What is a standard unit of alcohol?
10ml/8g of ethanol
How do you calculate how many units of alcohol are in a drink?
(% alcohol by volume x amount of liquid in millimetres) /1,000
What are the CAGE questions for alcohol dependency?
- Ever felt you should Cut down?
- Been annoyed by people telling you to cut down?
- Do you feel quilty about how much you drink?
- Eye opener: ever had a drink first think in the morning?
What is the doctrine of Dual effect?
If you administer a drug to relieve pain in doses that you know may be fatal, then provided your intention is not to shorten life but to relieve pain, the administration is not unlawful.
Normally, if you carry out an action knowing that X is a likely consequence of that act then the law regards you as intending to cause X.
What are the four principles of medical ethics?
Autonomy
Beneficence
Non-maleficence
Justice
What is Utilitarianism?
An act is evaluated solely in terms of its consequences. It acts to maximise good e.g. killing one to save many
What is Deontology?
The theory that the features of the act themselves determine worthiness
What is Virtue ethics?
These focus on the character of the person, integrating reason and emotion.
What is the PICO format?
- Population
- Intervention
- Comparator
- Outcome
When can you reject the null hypothesis?
When the P value is very small (less than 0.05)
Define epigenetics?
The expression of a genome depends on the environment
Define Allostasis?
The same as homeostasis
The stability through change of our physiological systems to adapt rapidly to change in environment
Define Allostatic load?
The long-term overtaxation of our physiological systems leading to impaired health (stress)
Define Salutogenesis?
Favourable physiological changes secondary to experiences which promote health and healing
What criteria should be used for prescribing antibiotics to someone with a sore throat?
CENTOR criteria
FeverPain score
Define Public Health?
The science and art of preventing disease, prolonging life and promoting health through organised efforts of society
What are the CENTOR criteria?
- Tonsillar exudate
- Absence of cough
- Tender or large cervical lymphadenopathy
- Fever
What are the three domains of public health?
- Health improvement
- Health protection
- Improving services
What are the key concerns of public health?
- Inequalities in health
- Wider determinants of health
- Prevention
What needs to be done/performed before a health intervention is made?
A health needs assessment
What is a health needs assessment?
- A systematic method for reviewing the health issues facing a population
- Leading to agreed priorities and resource allocation that will improve health and reduce inequaltities
What are the 3 different approaches of health needs assessments?
- Epidemiological
- Comparative
- Corporate
Define need?
Ability to benefit from an intervention
What is a health need and how is it measured?
- A need for health
- Measured using- Mortality, morbidity, socio-demographic measures
What are the 4 sociological perspectives of need?
- Felt need - individuals perceptions of variation from normal health
- Expressed need - individual seeks help to overcome variation in normal health (demand)
- Normative need - Professional defines intervention appropriate for the expressed need
- Comparative need - Comparison between severity, range of interventions and cost
What does an epidemiological approach to a health needs assessment involve?
- Define problem
- Look at the size of the problem – incidence/prevelance
- Services available – prevention/treatment/care
- Evidence base – effectiveness and cost-effectiveness
- Models of care – including quality and outcome measures
- Existing services – unmet need; services not needed
- Recommendations
What are the advantages of an epidemiological HNA?
- Uses existing data
- Provides data on disease incidence/mortality/morbidity etc.
- Can evaluate services by trends over time
What are the disadvantages of an epidemiological HNA?
- Quality of data variable
- Data collected may not be the data required
- Does not consider the felt needs or opinions/experiences of the people affected
What does a comparative approach to a health needs assessment involve?
Compares the services received by a population (or subgroup) with others:
- Spacial
- Social (age, gender, class, ethnicity)
What does the corporate approach to a health needs assessment involve?
- Ask the local population what their health needs are
- Uses focus groups, interviews, public meetings etc.
- Wide variety of stakeholders e.g. teachers, healthcare professionals, social workers, charity workers, local businesses, council workers, politicians
What is meant by the prevention paradox?
- A preventative measure which brings much benefit to the population often offers little to each participating individual
- i.e. it’s about screening a large number of people to help a small number of people
What is screening?
- A process which picks out apparently well people who are at risk of a disease, in the hope of catching the disease at its early stage
- NOT a diagnostic process – simply a means of assessing risk and catching diseases in their early stage
What is the sensitivity of a screening test and how do you calculate it?
The proportion of people with the disease who are correctly identified by the screening test
True positive / (true ive + false negative)
What is the specificity of screening and how is it calculated?
The proportion of people without the disease that are correctly excluded by the screening test
True negative / (true negative + false positive)
What is the positive predicted value and how is it calculated?
The proportion of people with a positive test result who actually have the disease
True positive / (true positive + false positive)
What is the negative predictive value and how is it calculated?
The proportion of people with a negative test result who do not have the disease
True negative / (true negative + false negative)
This is lower if the prevalence is higher
What is meant by lead time bias?
When screening identifies an outcome earlier than it would otherwise have been identified
This results in an apparent increase in survival time, even if screening has no effect on outcome
What is meant by length time bias?
A type of bias resulting from differences in the length of time taken for a condition to progress to severe effects that may affect the apparent efficacy of a screening method
What is human error?
A failure of a planned action or a sequence of mental or physical actions to be completed as intented.
What is Health?
Health is a state of complete physical, mental and social well-being (and not merely the absence of disease or infirmity)pp
What is True Positive?
Patients gave a positive screening result and subsequently tested positive for the disease
What is a False Positive?
Patients gave a positive screening result but were found not to have the disease in question after diagnostic tests
What is selection bias?
Error in assigning individuals to groups leading to differences which may influence the outcome.
Subtypes include - Sampling bias, volunteer bias, non-responder bias
What is publication bias?
- Failure to publish results from valid studies, often as they showed a negative or uninteresting result.
What is Expectation bias (Pygmalion effect)?
Only a problem in a non-blinded trial. Observers may subconciously measure or report data in a way that favours the expected study outcome
What is the Hawthorne effect?
Describes a group changing it’s behaviour due to the knowledge that it is being studied
What is late-look bias?
Gathering information at an inappropriate time e.g. studying a fatal disease many years later when some of the patients may have died already
What is procedure bias?
Occurs when subjects in different groups receive different treatment
What is lead-time bias?
Occurs when two tests for a disease are compared, the new test diagnoses the disease earlier, but there is no effect on the outcome of the disease
What is a Phase 0 clinical trial?
- Involves a small number of participants and aim to assess how a drug behaves in the human body.
What is a phase 1 clinical trial?
Safety assessment. Determines side-effects prior to larger studies. Conducted on healthy volunteers
What is a phase 2 clinical trial?
Assessed efficacy. Involves a small number of patients affected by a particular disease.
Can be subdivided into
- 2a- assesses optimal dosing
- 2b assesses efficacy
What is a Phase 3 clinical trial?
Assesses effectiveness
- Typically involve 100-1000’s of people, often as part of an RCT
What is a phase 4 clinical trial?
- Postmarketing surveillance
- Monitors for long-term effectiveness and side-effects
What is a confidence interval?
A range of values within which the true effect of intervention is likely to lie.
What is Confounding?
Confounding refers to a variable which correlates with other variables within a study leading to spurious results.
When does confounding occur?
Occurs when there is a non-random distribution of risk factors in the populations
When can you control confounding factors?
- In the design stage of an experiment by randomisation
- In the analysis stage of an experiment, can be controlled for by stratification
What is Linear regression?
Linear regression may be used to predict how much one variable changes when a second variable is changed.
What is a funnel plot used for?
- A funnel plot is primarily used to demonstrate the existence of publication bias in meta-analyses.
What does a symmetrial, inverted funnel shape mean?
- Indicates that publication bias is unlikely
What does an asymmetrical funnel plot mean?
- Indicates a relationship between treatment effect and study size. Indicates either publication bias or a systematic difference between smaller and larger studies
What is a Box-and-whisker plot?
Graphical representation of the sample minimum, lower quartile, median, upper quartile and sample maximum
What is a histogram used for?
A graphical display of continuous data where the values have been categorised into a number of categories
What is a Forest plot used for?
Forest plots are usually found in meta-analyses and provide a graphical representation of the strength of evidence of the constituent trials
What is a Scatter plot used for?
Graphical representation using Cartesian coordinates to display values for two variables for a set of data
What is a Kaplan-Meier survival plot used for?
A plot of the Kaplan-Meier estimate of the survival function showing decreasing survival with time
What is a Hazard Ratio?
Similar to relative risk but is used when risk is not constant to time. It is typically used when analysing survival over time
What is incidence?
- Number of new cases per population in a given time period
What is prevalence?
Total number of cases per population at a particular point in time
What is Intention to treat analysis?
Method of analysis in RCTs in which all patients randomly assigned to one of the treatments are analysed together
What is standard deviation?
A measure of how much dispersion exists from the mean
What is numbers needed to treat?
A measure that indicates how many patients would require an intervention to reduce the expected number of outcomes by one
How do you calculate number needed to treat?
1/(Absolute risk reduction) and is then rounded to the next highest whole number
How do you calculate experimental event rate?
(Number who had particular outcome with the intervention) / (Total number who had the intervention)
How do you calculate control event rate?
(Number who had a particular outcome with the control/ (Total number who had the control)
How do you calculate absolute risk reduction?
May be calculated by finding the difference between the control event rate and the experimental event rate
What is Power of a study?
Probability of (correctly) rejecting the null hypothesis when it is false (i.e. it will not make a Type II error).
What is power influenced by?
- Sample size
- Meaningful effects size
- Significance level
What is reliability?
Used in statistics to imply consistency of a measure
What is validity?
Determined by whether a test accurately measures what it is supposed to measure
What is positive predictive value?
The chance that the patient has the condition if the diagnostic test is positive
What is Negative predictive value?
The chance that the patient does not have the condition if the diagnostic test is negative
What is the best method to avoid selection bias?
Randomisation
What is included in the Bradford- Hill Criteria?
- Strength
- Consistency
- Specificity
- Temporality
- Biologic gradient
- Plausability
- Coherence
- Experimental evidence
- Analogy
What can increase and decrease prevalence?
- Total number of existing cases ata aparticular point
- Increased by - identifying new cases, increasing risk risk factor and increased life expectancy
- Decreased by - Curing conditions, decreased risk factors
What can increase and decrease incidence?
Increased - screening and idenitifying new cases
Decreased - decreasing risk factors
What is a gold standard test?
Where the test produces minimal false positives and false negatives
Define stress?
Where the demands on the individual are greater than their ability to cope
Name 2 types of stress?
Eustress - Beneficial and motivational
Distress - Negative stress, damage and harmful
Name 5 signs of stress, 1 per section?
Biochemical - Cortisol
Physiological - Shallow breathing, raised BP, HCL produced
Behavioural - Over/under eating, anorexia, insomnia, alchol, smoking
Cognitive - Negative thoughts, poor concentration, worse memory, tension headaches
Emotional - Mood swings, irritability, aggression, boredom
Name 3 types of human error?
Errors of OMISSION –> Action was delayed/not taken
Errors of COMMISION –> Wrong action was taken
Erros of NEGLIGENCE –> Action/omission did not meet the standard
What are the 3 key theories of ethics?
- Deontology
- Virtue Ethics
- Utilitarianism/Consequentialism
Give 5 qualities of a doctor under virtue ethics?
1) Discernment (Ability to judge well)
2) Integrity (Being honest)
3) Compassion (Concern for others)
4) Conscientiousness (awareness and perception)
5) Trustworthiness (someone you can talk to in confidence)
What are some strengths of a cross sectional study?
Relatively quick/cheap
No long periods of follow up
Multiple outcomes and exposures can be studied
Can be used for large data sets
What are the weaknesses of cross-sectional studies?
Not suitable for rare diseases
Not suitable for diseases with a short duration
Difficulty to assess if exposure or outcome came first
Unable to measure incidence
