Public Health Flashcards
What are the GMC Duties of a Doctor?
Protect and promote health of patients and public
Provide good standard of practice and care
Recognise and work within limits of competence
Work with colleagues in way that best serves patient’s interests
Treat patients as individuals and respect dignity
What are the 3 domains of Public health?
Health Improvement - Social Interventions aimed at preventing disease, improving health and reducing inequality
Health Protection - controlling infectious diseases and environmental hazards
Improving Services - organising and delivering safe and high quality services
What are the determinants of health?
PROGRESS:
Place of residence
Race/Ethnicity
Occupation
Gender
Religion
Education
Socio-economic status
Social Capital/resources
What is the Inverse care Law?
the availability of medical or social caretends to vary inversely with the need of the population served
Define:
Equity
Horizontal Equity
Vertical Equity
Equity: What is fair and just
Horizontal equity: equal treatment for equal need
Vertical equity: unequal treatment for unequal need
What are the steps of the health needs assessment?
A systematic approach for reviewing the health issues affecting a population which leads to agreed priorities and resource allocation that will improve health and decrease inequalities
Needs assessment
Planning
implementation
Evaluation
What are some different types of health needs assessments?
Epidemiological
Comparative
Corporate
What are some different types of need?
Felt Need - individuals perceptions
Expressed Need - Seeking help to overcome something
Normative Need - professional defines the intervention
Comparative Need - Comparison between severity, range of interventions and cost
What are some different approaches to resource allocation?
Lick My Ear
Libertarian approach: Taking responsibility for own health, wellbeing and fulfilment of life plan + autonomy
Maximising principle: Concentrating resources on those who stand to gain the most
Egalitarian principle: Equal access, equality and justice in healthcare
What are some models of Change?
Health Belief Model
Theory of Planned Behaviour
Trans-theoretical Model
What is the health belief model
Health Belief Model (Becker 1974)
- Individuals must believe they are susceptible to the condition
- Must believe in serious consequences
- must believe taking action reduces risk
- must believe benefits of actions outweigh costs
What is the transtheoretical change model of behavioral change?
Precontemplation contemplation preparation action maintenance
What are the structural determinants of illness?
Social Class Material deprivation and poverty unemployment discrimination and racism gender and health
What is the biological Model?
Mind and body are treated separately
The body is like a machine that can be repaired
This privileges the use of technological interventions
It neglects the social and psychological dimensions of disease
What are the criteria for medical negligence?
What two rules help determine an outcome?
4 Criteria
Was there a duty of care?
Was there a breach in the duty of care?
Did the patient come to harm?
Did the breach cause the harm?
Bolam rule: Would a reasonable doctor do the same?
Bolitho rule: Would that be reasonable?
Define Morality
Concern with the distinction between good and evil or right and wrong
Define ethics
A system of moral principles and a branch of philosophy which defines what is good for individuals and society
What is utalitarianism/consequentialism?
An act is evaluated solely in terms of its consequences
maximises good and minimises harm
What is Kantianism/Deontology?
Features of the act determine the worthiness of the act
Following natural laws and rights
What is virtue ethics?
Focus is on the individual doing the action.
An action is only virtuous if the person is genuinely intending to do the right thing
What are the 5 focal virtues?
Compassion Discernment Trustworthiness Integrity Conscientiousness
What are the 4 principles of ethics?
Autonomy - The right to make your own informed decisions.
Beneficence - Always do good
Non-maleficence - Do no harm
Justice - Concerns fair distribution of services
What are used to assess the functional limitations in the elderly population?
Katz ADL (Activities of Daily Living)
IADL
Barthel’s ADL
MMSE
What do the Katz and Barthel’s ADL indexes assess?
An individuals ability to carry out activities of daily living such as:
Dressing
Bathing
Going to the toilet - and urinary and bowl continence
Getting in and out of bed
What does the IADL Index assess?
Instrumental activities of daily living: Use a telephone do laundry go shopping handle finances
What does the MMSE assess?
Immediate and orientation memory
Short term memory
language
What are some key challenges that are faced with an ageing population?
Strains on pension and social security - pensions will have a higher payout
Increased demand for health care
Increased demand for longer-term healthcare
Bigger need for trained health workforce
Ageing workforce
Perversive ageism
What is an acute illness?
A disease of short duration that starts quickly
and has severe symptoms (often can be cured)
What is a Chronic Illness?
A persistent or recurring condition, which
may or may not be severe, often starting gradually with slow
changes (can’t be cured but can be treated)
What is Polypharmacy?
The use of multiple medications or
administration of more medications than are clinically indicated
What is the chain of infection?
A susceptible host causative infectious organism Reservoir (somewhere to spread to) Portal of exit Mode of transmission Portal of entry New susceptible host
What are some protective infection control precautions?
Gloves and aprons and hand hygeine
Correct sharps manipulation
Correct clinical waste and linen handling
What are the different types of transmission?
Direct - Contact such as with STIs
- Faecal oral route - viral gastroenteritis
Indirect - Vector borne - malaria dengue
- Vehicle Borne - hep B
Airborne - Respiratory route - TB/legionella
What is stress?
Stress occurs when the demands made upon an individual are greater than their ability to cope
What is good stress?
Eustress - motivational and helpful
What is bad stress?
Distress - Damaging or harmful
What is the bodies stress response?
● Lungs – increased resp rate
● Blood flow – BP increases, HR increases
● Skeletal muscle – tenses
● Spleen – more RBCs discharged
● Skin – blood flow redirected to muscles and heart
● Mouth – mucous and saliva production decreases, dries
● Immune System – redistribution of WBCs
What is the stress illness model?
An individuals susceptibility to disease or illness is increased when an individual is exposed to stressors which cause strain upon the individual leading to psychological and physiological changes
What is Screening?
A process which sorts out apparently well people who probably have a disease from those who probably do not
What is the main purpose of screening?
Prevention of disease
What are the Wilson Jungner Criteria?
● it should be a serious health problem
● the aetiology should be well understood
● should be a detectable early stage
● should be an accepted treatment for the disease
● facilities for diagnosis and treatment should be available
● there can’t be an unmanageable extra clinical workload
● a suitable test should be devised for the early stage
● the test should be acceptable for the patients
● intervals for repeating the test should be determined
● there should be an agreed policy on whom to treat
● the cost should be balanced against the benefits
What is Primary Prevention?
Prevention of the disease occurring
eg. Vaccinations, Couch to 5k
What is Secondary Prevention
Early detection of disease in order to alter the course of the disease and maximise the chances of a complete recovery
Screening Programmes
What is Tertiary Prevention?
Preventing complications of the disease by slowing progression.
eg. Diabetic control/eye screening
Give some examples of Primary, Secondary, and Tertiary Prevention for Type 2 Diabetes
Primary - reduce risk factors by losing weight, having a balanced diet, increasing physical exercise
Secondary - Medications such as metformin, bariatric surgery to treat the condition and prevent progression
Tertiary - Population screening - diabetic eye screening
What is an error?
Any preventable event that may cause or lead to patient harm
What is Neglect?
Falling below the acceptable standard of care
What are violations?
Deliberate deviations from practices, procedures and standards or rules
What are the possible outcomes of errors?
An Adverse Event
A Near Miss
What are the different types of error?
Errors of Omission
Errors of Commission
Errors of Negligence
What are errors of Omission
When the required action is delayed or not taken
What are errors of Commission?
When the wrong action is taken
What are errors of Negligence?
When the actions or omissions do not meet the standard of an ordinary skilled person professing
What are some examples of errors of negligence?
Skill based Errors
Slips and lapses – when the action made is not what was intended
Rule/Knowledge Based Errors
An incorrect plan or course of action is chosen
How can errors be managed?
At an individual level or organisational level
What is individual error management?
Errors are the products of wayward mental processes of individual people in the system
What is organisational error management?
Adverse events are the product of many causal factors (swiss cheese model) and so the whole system is to blame.
Define Prevalence?
The proportion of a population that are found to have the disease at one point in time
Define Incidence?
The number of new cases of a a disease arising within a specified time period
When can you breach confidentiality?
When required by law
When the patient provides consent
When it is in the public interest
What are the criteria for disclosure when breaching confidentiality?
Anonymous Patients consent Kept to a necessary minimum Meets current law After death confidentiality continues
How would you approach a patient about quitting smoking?
3 As
Ask
Advice
Assist
Give 4 examples of UK screening programmes
Antenatal and Newborn screening
Diabetic Eye screening
Cervical Screening (25-49 every 3 years and 50-70 every 5 years)
Breast screening (>50 every 3 years)
Bowel Cancer (>60 every 2 years)
Abdominal Aneurysm Screening (men >65 yrs self refer)
What is Sensitivity?
The proportion of people with the disease who are correctly identified by the screening test
(TP / TP + FN)
What is Specificity?
The proportion of people without the disease who are correctly excluded by the screening test.
(TN / FP +TN)
What is the Positive Predictive Value?
The proportion of people correctly identified as having the disease
(TP / TP + FP)
What is the Negative Predictive Value?
The proportion of people correctly identified as not having the disease
(TN / FN + TN)
What is the role of the doctor in combating health inequalities?
Changing systems Changing perspectives changing education working hollistically advocating on the social determinants of health
What are the social determinants of health?
Societal factors which influence an individuals health
What are the social determinants of health based on?
Fair society and healthy lives - the marmot report (2010)
Give some examples of social determinants of health
Education housing income access to care occupation
Why are social determinants of health important?
Health problems are worse in more unequal societies
Above a certain level, health ceases to improve in proportional and income disparities within a country affect health
Despite equal access to healthcare in the UK, health outcomes are not equal within society.
What is the Black Report?
From 1980
Stated that health inequalities are affected by:
Material - environmental causes
Artifact - there are not inequalities, it is how it is measured
Cultural/behavioral - poorer people behave in unhealthy ways
Selection - sick people sink socioeconomically
What is the Marmot Report?
From 2010
Health inequalities are a matter of faireness and social justice
There is a social gradient in health - the lower a persons social position the worse their health
Action should focus on reducing the gradiant in health.
What is proportionate Universalism?
Part of the Marmot report
Focusing on the most disadvantaged will not reduce health inequalities
Any action taken must be universal
Must be scaled with intensity proportional to the disadvantage
What health inequalties require action on according to the Marmot Report?
Give every child the best start in life
Enable all children, young people and adults to maximise their capabilities and have control over their lives
Create fair employment and good work for all
Ensure health standard of living for all
Create and develop healthy and sustainable places and communities
Strengthen the role and impact of ill health prevention
What is nudge theory?
Changing the environment to make the healthy option the easiest option
What are the millennium development goals?
- Eradicate Poverty and Hunger
- Universal Primary Education
- Gender equality
- reduce child mortality
- improve maternal Health
- Combat Malaria and HIV and other diseases
- Ensure environmental sustainability.
- Develop global partnerships for development
Define Probability
How likely an event is to happen
Define odds Ratio
A Ratio of odds relative to two groups
Define Risk
Probability of an event occurring within a given time period
Define Absolute Risk
The risk of developing a disease over a certain time
Define Relative Risk
The risk of developing a disease in one category compared to another
Eg. lung cancer in smokers vs non-smokers
What is absolute risk reduction?
Attributable risk:
The rate of risk reduction due to the exposure
(incidence exposed - incidence non-exposed)
What is number needed to treat
The number of people needed to treat to save one life
1/absolute risk reduction
What are confidence intervals?
The range of values that are believed to contain the true parameter value
What are confounding variables?
effects of 2 or more variables on one another
What are some types of screening?
Population-based
Oppotunistic
Screening for Communicable diseases
Pre-employment
opportunistic
What types of bias are screening tests affected by?
Selection bias
Lead time bias
Length time bias
What is Selection Bias?
The people who choose to participate in screening programmes may be different from those who don’t; proper randomisation is not achieved.
What is Lead time bias
Screening identifies diseases earlier and therefore gives the impression that survival is prolonged but survival time is actually unchanged.
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.
Give some general examples of Primary, Secondary and Tertiary Prevention
Primary - risk factor awareness, immunisations
Secondary - Screening, reducing impact of early-stage disease
Tertiary - Medications to prevent progression, Rehabilitation
What is the hierarchy of the study designs pyramid?
Top: Systematic reviews + meta-analysis Clinical Trials (RTCs) Observational studies (Cohort, Cross-sectional, Case-control) Case Reports / Case series Anecdotal findings, opinions, or ideas Bottom
What are the types of descriptive observational studies?
Individuals - Case report / Case series
Populations - Ecological study, Cross-sectional study
What are the types of analytical observational studies?
Cross-sectional
Case-Control
Cohort
What is the Bradford-Hill Criteria?
The minimum set of conditions necessary to provide adequate evidence of a causal relationship
What are some methods of collecting qualitative data?
Interviews,
Focus groups
Observation
What is the concept of medicalisation?
When aspects of normal life become the focus of medicine and intervention, medical problems/conditions are thus created.
What are the 3 main behaviours relating to health and what do they mean?
Health behaviour - Behaviour aimed at preventing disease
Illness behaviour - Behaviour aimed at seeking a remedy
Sick role behaviour - Behaviour aimed at getting well
What can health behaviours be?
Health Damaging - eg. smoking
Health Promoting - eg. exercise
Why is it important to understand health behaviours?
For adequate measures in disease prevention
For assessing where funding should be aimed
For understanding where interventions are best placed (at individual and population-based levels)
Give some examples of health promotion campaigns
Change 4 life Movember Dry January Screening Promotion F.A.S.T
What is unrealistic optimism?
When individuals continue to practice health-damaging behaviours due to inaccurate perception of risk and susceptibility
What are some examples of theories of behavioural change?
Health belief model
Theory of planned behaviour
Transtheoretical model
Nudging
What factors are important to consider when promoting behaviour change?
How personality and behaviour interact
Assessment of risk perception
chan ging societal norms
What is the WHO definition of health?
Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity
What are some social influences on health?
Life expectancy decreases as social class decreases Gaps between upper and lower class are rising
What determines population health?
The extent of income division within a society. Therefore more unequal societies have worse health
What is Sociology?
The study of social relations (bonds between people or groups of people) and social processes. It is the measure of social interdependencies.
What are the social roles of a sick person?
Exempt from normal social roles
not responsible for their condition
should try to get well
should seek help from and co-operate with the medical profession
What is Iatrogenesis?
The unintended adverse effects of a therapeutic intervention.
They can be clinical, social or cultural
What is the effect of prevalence of a disease on screening results?
A high disease prevalence would mean the incidence of false positives falls. The positive predictive value therefore increases and the negative predictive value would decrease
What are some benefits to screening?
Prevent suffering
early identification is beneficial
early treatment is cheaper and often more effective
Patient satisfaction tends to be high
What are some negatives to screening?
Damage caused by false positives and false negatives
Adverse effects of screening tools on healthy individuals
Personal choice is compromised
What is the prevention paradox?
A preventative measure that brings a lot benefits to population, often offers little to each participating individual
Why does high-risk approach to screening favour those who are more affluent and better educated?
More likely to engage with health services
More likely to comply with treatments
More likely to have the necessary means to change their lifestyle
Define Outbreak
Define Epidemic
Define Pandemic
Outbreak: a number of cases that exceeds what would be expected
Epidemic: Cases occurring in the same geographical location
Pandemic: disease that has spread over countries or continents affecting large numbers of people
Give some notifiable diseases
Acute encephalitis
Acute meningitis
Anthrax
Cholera
HUS
Malaria
Meningococcal Septicaemia
Rabies
Scarlet Fever
Tetanus
Whooping Cough
Acute Infectious Hepatitis
Poliomyelitis
Botulism
Diphtheria
Leprosy
Measles
Mumps
Rubella
Smallpox
Tuberculosis
Yellow Fever
What percentage of deaths in the UK are attributed to CHD?
Roughly 40%
1 in 5 men
1 in 8 women
What are the unmodifiable risk factors of CHD?
Sex Age Ethnicity Family Hx Early life circumstances
What are the potentially modifiable risk factors of CHD?
Physiological/clinical:
High cholesterol
Hypertension
T2DM
Lifestyle: Smoking Physical Inactivity Overweight Poor nutrition Alcohol
What is the Primary prevention of CHD?
Lifestyle changes (SNAP)
Smoking, Nutrition, Alcohol, Physical Activity
Medical (anti-hypertensives, Statins, Metformin/insulin)
Cardiac Rehabilitation
What is the secondary prevention in CHD?
Primary care CHD registers Medical Management (Apsirin, ACE Inhibitors, Statins) Phase 4 cardiac Rehabilitation
What are some psychosocial influences in CHD?
Personality Depression Anxiety Work Social Support
Give some general facts about smoking
Men smoke more than women
Smoking prevalence is decreasing
Lower Socioeconomic groups smoke more
What government rules have been put in place to reduce smoking?
2005 - Ban smoking in public places
2007 - Minimum age was raised to 18
What are some reasons that people smoke?
Habit
Stress
Nicotine addiction
Socialisation
What are some forms of nicotine replacement therapy?
Patches Gums Nasal Spray lozenges All available on the NHS
What is Influenza?
Flu that is spread via coughing, sneezing and touch.
Incubation period is 1-3 days
Infectious with symptom onset 4-5 days
Which influenza causes pandemics and which influenza is seasonal?
Type A - Pandemics
Type B - Seasonal
What virus family does influenza come from?
Orthomyoxoviridae
What are the surface antigens of influenza?
Haemagglutinin
Neuraminidase
What are the criteria for pandemic spread?
Novel virus Capable of infecting humans Capable of causing illness in humans Large pool of susceptible people Ready and sustainable transmission from people
What are the phases of a pandemic?
Phases of a pandemic:
● Phases 1-3 (mostly animal infections with few human infections)
● Phase 4 (sustained human to human transmission)
● Phases 5-6 ( Widespread human infection)
● Post peak (possibility of recurrent events)
● Post pandemic (disease returns to seasonal levels)
What are some diseases that cause diarrhoea?
Dysentry
Typhoid
Hepatitis
Cholera
What are some Causative organisms of Diarrhoea?
Rotavirus Shigella E.coli Salmonella Typhi Campylobacter Norovirus Clostridium Difficile
What is S.I.G.H.T?
Prevention of C.Diff: Suspect C.diff Isolate the case Gloves Hand wash Test stool for toxin
Treat with Metronidazole or Vancomycin
Why is diarrhoea in children important?
Kills more children than AIDS malaria and measles combined
Prevention is via a package from WHO-UNICEF
Fluid replacement therapy and Zinc treatment
Who are at risk of diarrhoea?
Poor hygiene
children at pre-school/nursery
Those preparing uncooked foods
Health care and social workers
What are the limits for alcohol?
14 units a week for men and women
Pregnant women recommended not to drink
What is a standard unit of alcohol?
10mL/8g of ethanol
(% alcohol by Volume X amount of liquid in mL) / 1000
What are some social implications of Alcohol?
Violence rape depression anxiety driving offences
What are the CAGE Questions for alcohol dependency?
Ever felt like you should CUT down?
Been ANNOYED by people telling you to cut down?
Do you feel GUILTY about the amount you drink?
EYE OPENER - Ever had a drink first thing in the morning?
What is concordance?
Patients and the doctors are in an open discussion about the treatment decisions which is aimed to increase compliance of patients taking treatments
What are some reasons for non-compliance?
Disagree with doctor
Cost
Side-effects
Forgetful (psych/neuro/chronic diseases)
Lack of understanding of importance
Barriers to healthcare
Intentional - the patient has their own beliefs about their condition or treatment
What is adherence?
the extent to which patient actions match AGREED recommendations
Still recognises the doctor as the expert but acknowledges importance of patient beliefs
What is Compliance?
the extent to which the patient’s behaviour coincides with medical or health ADVICE, a paternalistic relationship
Paternalism means the patient must follow the doctor’s orders, not taking into account their views
What is Palliative Care?
Palliative care improves the quality of life of patients and families who face life-threatening illness by
providing pain and symptom relief, spiritual and psychosocial support from diagnosis to the end of life
and bereavement.
What is the difference between Specialist palliative care and generalist palliative care?
Specialist:
HCPs who specialise in palliative care within an MDT. often used for patients with cancer.
Generalist:
Available to anyone with advanced progressive disease likely to end in death. Provided by GPs. district nurses, hospital doctors, social workers etc.
What is ethics?
The attempt to arrive at an understanding of the nature of human values of how we ought to live and of what constitutes right conduct
What is Top Down Deductive?
Where one specific ethical theory is consistently applied to each problem
What is Bottom Up Inductive?
Using past medical problems to create guidelines to practice
What is the doctrine of dual effect?
If you carry out an action knowing that X is a likely consequence of that action. Then in the eyes of the law you are regarded as intending to cause X
What is validity?
How close to the truth something is
What is Reliability?
How consistent the results are
What is Applicability?
How relevant a study is to clinical medicine
What is positive Skew?
Tail to the right
The mode is less than the median which is less than the mean
(household income)
What is negative skew?
Tail to the left
The mode is greater than the median which is greater than the mean
(age of death)
What are Glaser and Strauss (1965) 4 awareness contexts?
Closed awareness
Suspicion awareness
Mutual pretense
Open Awareness
What is closed awareness?
When the patient is unaware of their own impending death but others (staff and family) are aware
What is suspicion awareness?
The patient suspects that they are dying and tries to seek confirmation of this
What is Mutual pretense?
Everyone knows the patient will die including the patient but it is not discussed
What is Open awareness?
Everyone knows the patient is likely to die and talks openly about it
What is the sequence of the stress response?
Alarm
adaptation
exhaustion
What is cost utility analysis?
describes outcomes measured in quality adjusted life years e.g. incremental cost per QALY gained. It is the most common economic evaluation in health.
What is economic efficiency?
when resources are allocated between activities in such a way as to maximise profit and is NOT a type of economic evaluation.
what is cost effective analysis?
describes outcomes measured in natural units e.g. incremental cost per life year gained.
what is cost benefit analysis?
describes outcomes measured in monetary units e.g. net monetary benefit.
what is minimilisation analysis?
describes outcomes measured in any units and are the same in both treatments (and therefore just minimise cost).
how do you work out the incremental cost effectiveness ratio for a new drug?
ICER = difference in costs/difference in benefits.
eg. Difference in costs would be £25,000-£10,000 = £15,000. Difference in benefits is 6 QALY – 5 QALY = 1 QALY. £15,000/1 = £15,000 per QALY gained.
What are the big 5 CAM (complementary and alternative medicine)
Acupuncture, chiropractic herbal medicine homeopathy osteopathy
What is a sample?
A selection from a population which aims to represent the whole population.
Name some types of bias and explain
Sampling bias, some people are more likely to be included in your sample than others. (omission, inclusive bias)
Recall bias, people cannot remember information correctly
Social- desirability bias, change answers to more acceptable ones
Information bias, errors in your measurements.
What is a confounding factor?
Risk factors other than those being studied that influence the outcome
What are the categories of studies?
– Experimental vs. Observational
– Retrospective vs. Prospective
– Individual vs. Population level
What is an experimental research method?
One where the researcher has made some kind of intervention eg crossover trial or RCT
What is an observational study?
There is no intervention data is just collected about what happens, E.g. case-control, cross-sectional,cohort,ecological studies
What is a retrospective study?
One which looks back at what has already happened case-control
What is a prospective study?
Collect information then follow up over time Cohort study
What is an individual study?
Collect information about individuals all studies except ecological.
What is a popilation study?
Talk about a whole population
What is the ecological fallacy
making inferences from populations about an individual.
Describe case-control studies
Find individuals with the outcome and a similar group without and take a random sample of each and see who had the eposure compared to others.
What are the strengths and weaknesses of case-control studies?
Strengths: Quick and inexpensive suitable for rare diseases multiple exposures can be measured suitable for measuring outbreaks
Weaknesses:
Only a single disease can be measured
not suitable for rare exposures
need data before the study (retrospective study)
affected by selection bias and confounding variables
Describe a cross-sectional study
Investigates what is happening at the current time.
Outcomes and exposures are measured simultaneously
What are the strengths and weaknesses of a cross-sectional study?
Strengths:
fast and inexpensive
rapid feedback on current events
multiple outcomes and exposures can be studied
Weaknesses
not suitable for rare diseases
limited potential to establish disease aiteology
affected by selection bias and confounding variables
Describe a cohort study
Collect information on a sample and follow- up over time to explore who gets the outcome
What are the strengths and weaknesses of a cohort study?
Strengths:
useful for demonstrating casual affects
multiple diseases can be studied
multiple exposures can be studied
Weaknesses:
expensive and time-consuming
not suitable for rare diseases
need to deal with confounding factors
Describe a RCT?
Have multitple groups with different exposures compare the outcomes to get a causal relationship.
What are the strengths and weaknesses of an RCT?
Strengths:
most convincing evidence for cause and effect
The gold standard for evaluating interventions
weaknesses: expensive not always practical for showing long term effects can be affected by non-compliance not always ethical
What is a crossover trial?
an extension to an RCT. everyone does all the arms of the study. which reduces confounding even more as each person can be compared across the arms. thre can be carry-over effects and more technical analyses
What steps should be taken in an RCT to minimise bias?
Blinding, randomisation, placebos, matching
What are the two main groupings for variables?
Categoric and numeric
What are the types of categoric variables?
Binary, ordinal, nominal
what are the numeric variables?
Discrete and continuous
What is the odds?
number with the outcome/ number without the outcome
How can you quantify differences?
Risk differences, risk ratios, absolute risk, and relative risk.
What is risk difference?
the difference between the two risks you have calculated
What is a risk ratio?
divide one risk by the other. the top group is the focus group compared to the other one.
How do you interpret a risk ratio?
RR> 1 the focus risk is higher
RR=1 the two groups are the same
RR<1 the focus risk is lower than the other
1 is no difference
How can you swap the focus of the risk ratio is?
inverse 1 divide by it
What is odds ratio?
Odds divided by odds
How do you interpret odds ratio?
> 1 – Greater odds of associated with exposure and outcome
=1 – No association
<1 – Lower odds of association between exposure and outcome
Eg. Odds ratio of 0.8 = 20% decrease in odds
Why might you use risk ratio?
It puts it in context more
Why do we use Odds ratios?
they are useful for some statistical methods
If something is very rare how does OR and RR compare?
RRroughly= to OR for rare outcoumes
If something is more prevalent what happens to RR and OR?
it makes the OR a poor approximation of the RR
What is the median
middle value in sequential order
What is positive skew?
where the peak is to the left
the mean is greater than the median which is greater than the mode
What is negative skew?
most of the values are to the right,
the mean is less than the median which is less than the mode
How to decide which measure of spread to use?
if it is symmetric and normally distributed (with the median and mean close together) then use mean and SD
Otherwise use median and IQR as they are less affected by skew
What is the use of the normal distribution?
The sd can tell you about percentage certainty
What are the limits of correlation coeffiecient?
-1 = perfect negative correlation 0 = no linear relationship \+1 = perfect positive correlation
What is standard error?
How well your sample representing the population.
How can standard error be reduced?
Enlarging the sample size the more similar the people are.
What is the formula for the standard error of a mean?
SD/root(n)
What is the difference between standard error and standard deviation?
Standard deviation is a descriptive value about the data collected
Standard error is an inferential number about how well our estimate represents the true population value
What is the use of confidence interval?
It is often used as a comparative value between data sets. can be used for inferential statistics
What are confidence intervals?
The true value is quite certain to lie between those two points.
What are confidence interval calculated from?
Standard error and SD values
What is the null hypothesis?
There is no link between the two variables
What is a p value?
A p-value measures the probability of obtaining the observed results, assuming that the null hypothesis is true
The probability that the mean could be from the standard deviation.
If mean is close to the null what will the p value be?
Close to one
How should you phrase rejecting the null hypothesis?
The evidence suggests to reject the null hypothesis
What is the generally accepted significant p value?
p=0.05 for statistical significance
What is another significance test?
One sample t test, two sample t test, chisquare tests, ANOVA test, Pearson correlation coefficient
What is regression?
Plotting the correlation between variables using y=a+bx
What is the effect of using multivariable method?
It accounts for the effect of confounding factors
How can you appraise the study design?
Who is studied? are there missing groups over sampling? is it clear what the aim is
What can you appraise the descriptive statistics?
Summariesed data appropriately, Normal distribution, SD
What can you appraise the inferential statistics?
p values CI did they look at normality test
A 25-year-old woman presents to a general practitioner reporting
that she is suffering from stress and has recently been having increased
negative thoughts and poor concentration. What type of stress response is
this patient experiencing?
Cognitive: Cognitive signs of stress - Negative thoughts; Loss of
concentration)
An elderly man presents to his general practitioner reporting that he
is suffering from stress. On examination the GP notices that the patients’
blood pressure is raised and his breathing is shallow. What type of stress
response is this patient likely to be experiencing?
Physiological: Physiological signs of stress - shallow breathing;
Raised blood pressure; Increase in acid production in the stomach)
A 42-year-old woman has attended her general
practitioner reporting that she is suffering from stress. She says
that she very tearful, has been increasingly irritable with her
partner and has had mood swings. What type of stress response
is this patient experiencing?
Emotional: Emotional signs of stress - Mood swings;
Tearful; Irritable; Aggressive; Apathetic
Which term would best describe: The total number of UK
adults with a BMI greater than 30 (i.e. obese) at a given time?
Prevalence: Proportion of a population with a
disease/condition at a point in time
Which term would best describe: The detection of early
disease in order to alter its course, for example cancer screening and
the early identification of heart disease?
Secondary prevention: Early detection of disease, followed
by appropriate intervention
Which term would best describe: The number of
diagnosed cases of alcohol related liver disease per
100,000 in England during 2009.
Incidence: Rate at which new cases occur in a
population in a certain time period
Which type of study design below would be best to investigate
the following; to identify patients who have had heart attacks and
compare their diet, smoking habits and exercise activity with people
that are similar to them except that they have not had heart attacks?
Case control: Observational study of persons with the
disease of interest and a suitable control group (without disease).
Analysis of events that occurred before onset of disease
(retrospective
A new drug has been developed to reduce blood pressure and the
drug manufacturer wants to measure its clinical effectiveness in the very
elderly. A professor in care of the elderly agrees to run a research study. In
order to have enough power he will need to recruit patients from the clinics
of other hospitals as well his own patients. Which type of study design would
be most appropriate?
RCT: Investigation involving intentional change in some aspect of
the status of the subjects; randomisation of subjects to intervention and
control conditions)
What aspect of the relationship between occupation and
asthma could only be examined through prospective studies?
(Causation: The existence of a causal relationship between
variables; the cause must precede the effect
If these figures came from an analysis of time to
infection (mean= 2.5, median= 1.2, SD=2, IQR= 0.6 to
2.8); which would you expect to see published in the
article:
There is a big difference between mean and
median, so not normally distributed. That leads to median,
and IQR goes with the median
In a small randomised trial of a new treatment in type 2
diabetes, the mortality in the treated group was half that in the
control group, but the difference was not significant. We can
conclude that:
The treatment shows promise (half the mortality) but
we need a larger size to make sure the difference is not by chance
The Odds Ratio (OR) of death for a new treatment
compared to placebo is 0.51 (95% 0.30, 0.83). This
means:
There is a 49% reduction in the odds of death for
treatment vs. placebo
Which of the following is true about linear regression:
A. The predictor variables can be only numeric
B. The outcome variable is binary (yes/no)
C. Can only explore the joint associations between two variables
D. Can remove background associations to reveal a clearer picture of
the relationship between the main exposure of interest and outcome
E. Cannot produce confidence intervals for the coefficients
Can remove background associations to reveal a clearer picture of
the relationship between the main exposure of interest and outcome
What is prevalence probability?
The probability of having a disease at a given point in time
What is incidence probability?
The probability of getting a disease during a specified point in time
What is the incidence rate?
The average rate of change over time
What is the hazard rate?
Instantaneous rate of change.
What is conditional probability?
The probability that something will happen given that an event has already happened
What are odds?
The probability that an event will occur.
Range between 0 and 1
What is length time bias?
Conditions with a longer duration are more likely to be captured in prevalence.
Drug A has a risk of 0.6
Drug B has a risk of 0.2. of causing heart attacks
What is the risk difference
What is the risk Ratio
What is the absolute risk difference
What is the relative risk difference
Risk difference = 0.4 (0.6-0.2) and therefore is 40%
Risk Ratio = 3 (3x the risk of drug A than B)
Absolute risk = 0.4 (A-B)
Relative risk difference = (A-B)/B *100 = 200%
What information does risk difference provide?
An absolute measure of the association of exposure on disease occurrence
Gives a clear sense of public health impact
What information does risk ratio give?
Gives a relative measure
Gives a clear sense of the strength of the effect
What is an association?
A statistical link between exposure and disease.
may not reflect a cause and effect relationship
What is a Causation?
A statistical link where a disease is directly caused by exposure.
How can sample variability be measured both within a sample and between a sample?
Within a sample - use the SD
Between a sample - Use the SE
What do 95% confidence intervals mean?
That 95% of the data falls within 2 SDs of the mean and this contains the true mean value.
What is an application of regression?
Develop a model for risk prediction of a clinical outcome
What is the difference between crude and adjusted effects?
Crude effects do not take confounding variables into account whereas adjusted does.
What form are regression lines written in?
Y= a + bx Y= Continuous outcome a = intercept b = coefficient (slope) x = explanatory (predictor value) variable
What is the bradford hills criteria?
Criteria used to support a causal association
- Plausibility: reasonable pathway to link exposure to outcome
- Consistency: same results if repeated at different times with different people/geographical location
- Temporality: exposure precedes outcome
- Strength: with or without a dose response relationship
- Specificity: causal factor relates only to outcome in question
- Change in risk factor: incidence drops if risk factor is removed
