PH Flashcards
4 types economic evaluation
Cost-effectiveness analysis (CEA)
Cost-utility analysis
Cost-benefit analysis:
Cost-minimisation analysis
Cost-effectiveness analysis
Outcomes are measured in natural units (e.g. incremental cost per life year gained)
Cost-utility analysis
Outcomes are measured in quality adjusted life years (e.g. incremental cost per QALY gained)
Cost-benefit analysis:
Outcomes are measured in monetary units (e.g. net monetary benefit)
Cost-minimisation analysis:
Outcomes (measured in any units) are the same in both treatments. This is used when the aim is only to minimise costs.
incremental cost-effectiveness ratio (ICER)
cost-effectiveness can be summarised in terms of an incremental cost-effectiveness ratio (ICER)
he incremental costs of one treatment over another, divided by the incremental effects. So, if a new treatment produces 10 additional years of life more than current treatments and costs £10,000 more than current treatments, its ICER is 10,000 divided by 10, or £1,000 per life year gained.
The ICER, therefore, combines cost and outcome data in a simple summary measure. Treatments with lower ICERs produce units of health (e.g. life years) at lower cost than treatments with higher ICERs. As such, they are said to be more cost-effective
calculate QALYs
multiply the length of life expected to be gained by the new treatment or invention, by the quality of life a patient can expect to have.
how is quality of life measured?
on a 0 - 1 scale and this score represents the value of different levels of health. We’ll be exploring what these numbers mean and where they come from later on in this course.
We can think of a single QALY as being equivalent to one year in perfect health.
How do we find the ‘Q’ in QALYs
There are a number of elements required in order to do this:
We need to describe the health state that is going to be valued.- usually done using PROMs e.g. EQ 5D DL
We need a way to value the health state that we have described.
We need a group of people to provide the values.
A patient lives in a health state with a quality of life of 0.4 for 2 years, followed by a health state with a quality of life of 0.2 for 5 years, how many QALYs is this?
1.8
opportunity cost
The health benefits for patients that will be foregone if a new treatment is funded
obesogenic environemnt
physical: car culture
economic: expesive fruit and veg
sociocultural: family eating patterns
the runaway wt gain train
obesogenic environment=steep slope
knowledge, prejudice, phsyiology=ineffective brakes
vicious cycles mechanical dyfunct, psychological impact, ineffective deiting, low socioeconomic status=accelerators
mechanisms that maintain being overwt
physical: more wt=more difficult to exercie and dieting (metabolic response)
psychological: low self esteem, guilt, comfort eating
socioeconomic: rediced opportunities, employmeny, relationships, social mobility
epigenetics
The expression of a genome depends on the environment
allostasis
same as homeostasis
The stability through change of our physiological systems to adapt rapidly to change in environment
allostatic load
Long-term overtaxation of our physiological systems leading to impaired health (stress)
salutogenesis
Favourable physiological changes secondary to experiences which promote healing and health
role or primary care
Managing illness and clinical relationships over time
Finding the best available clinical solutions to clinical problems
Preventing illness
Promoting health
Managing clinical uncertainty
Getting the best outcomes with available resources
Working in the primary health care team
Shared decision making with patients
dangers of over prescribing abx
Unnecessary side effects
Medicalisation of self-limiting conditions
Antibiotic resistance
centor criteria
Tonsillar exudate
Absence of cough
Tender or large cervical lymphadenopathy
Fever
public health
the science and art of preventing disease, prolonging life and promoting health through organised efforts of society
3 domains of public health
Health improvement
Health protection
Improving services
key concerns of public health
Inequalities in health
Wider determinants of health
Prevention
health improvement
Societal interventions:
Inequalities
Education
Housing
Employment
Lifestyles
Family/community
Surveillance and monitoring of specific diseases and risk factors
health protection
Measures to control infectious disease risks and environmental hazards:
Infectious diseases
Chemicals and poisons
Radiation
Emergency repsonse
Environmental health hazards
improving services
organisation and delivery of safe, high quality services for prevention, treatment and care:
Clinical effectiveness
Efficiency
Service planning
Audit and evaluation
Clinical governance
Equity
applying health interventions
Delivered at an individual level (i.e. vaccinations to prevent an individual from getting ill)
Delivered at a community level (i.e. opening a new outdoor play area in a particular town)
Delivered at a population level (i.e. putting iodine in salt to prevent iodine deficiency)
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 inequalities
diagram for health needs assessment
needs assessment ->planning ->implementaion ->evlauation ->repeat
3 approahes of health needs assessment
Epidemiological
Comparative
Corporate
define need
Ability to benefit from an intervention
define demand
what people ask for
health need and measurement
A need for health
Measured using - mortality, morbidity, socio-demographic measures
health care need
A need for healthcare – the ability to benefit from health care
Depends on the potential of prevention, treatment and care services to remedy health problems
felt need
individual 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 some potential sources of data for an epidemiological HNA?
Disease registry
Hospital admissions
GP databases
Mortality data
Primary data collection (e.g. postal/patient survey
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)
i.e. COMPARES THE SERVICES FOR A PARTICULAR HEALTH ISSUE IN TWO DIFFERENT AREAS
What factors might a comparative HNA examine?
Health status
Service provision
Service utilisation
Health outcomes (mortality, morbidity, quality of life, patient satisfaction)
What are the advantages of a comparative HNA?
Quick and cheap if data available
Indicates whether health or services provision is better/worse than comparable areas (gives a measure of relative performance)
What are the disadvantages of a comparative HNA?
May be difficult to find comparable population
Data may not be available/high quality
May not yeild what the most appropriate level (e.g. of provision or utilisation) should be
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 are the advantages of a corporate HNA?
Based on the felt and expressed needs of the population in question
Recognises the detailed knowledge and experience of those working with the population
Takes into account wide range of views
What are the disadvantages of a corporate HNA?
Difficult to distinguish “need” from “demand”
Groups may have invested interests
May be influenced by political agendas
Define primary prevention and give an example
Preventing disease before it has happened
Examples – change4life, 5 a day
Define secondary prevention and give an example
Catching a disease in its early or pre-clinical phase
Example – breast screening programme (and all screening)
Define tertiary prevention and give an example
Preventing complications of a disease
Example – diabetic foot care, reviews for eyes in diabetic patients, attending physio/rehab after a stroke to prevent immobility and aspiration pneumonia
What are the 2 general approaches to prevention?
Population approach – preventative measures e.g. dietary salt reduction through legislation to reduce BP, adding iodine to salt to prevent iodine deficiency
High risk approach – identifying individuals above a chosen cut-off and treat e.g. screening for hypertension,
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 are the Wilson and Junger criteria needed for a screening programme?
The disease must be an important problem
The disease must have a known and detectable latent phase
The disease must have a known natural course/progression
There must be a test which is acceptable to the population
There must be a treatment for the disease
There must be an agreed at-risk population of which to screen
There must be an agreed policy on who to treat
The costs of the screening should be economically balanced
What are the different types of screening?
Population-based screening programmes (e.g. cervical cancer, breast cancer)
Opportunistic screening (e.g. performing BP measurements in GP)
Screening for communicable disease
Pre-employment and occupational medicals
Commercially provided screening (where you can pay to get your blood sent off and tested for all sorts of genetic problems)
Genetic counselling (i.e. genetic testing for people with FHx of genetic disease)
What are some disadvantages of screening?
Exposure of well individuals to distressing or harmful diagnostic tests
Detection and treatment of sub-clinical disease that would never have caused any problems
Preventative interventions that may cause harm to the individual or population
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 positive + false negative)
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 positive + false negative)
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)
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)
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
Define incidence?
The number of new cases of a disease in a population (e.g. per 100,000) in a given time frame (e.g. per year)
define prevalence
The total number of people with a condition per 100,000 per year
Number of existing cases/population/point in time
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
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
descriptive study design
Case reports or case series – study individuals
Ecological studies – use routinely collected data to show trends in data and thus is useful for generating hypotheses. Shows prevalence and association, cannot show causation
cross sectional study
Divides populations into those without the disease and those with the disease and collects data on them once at a defined time to find associations at that point in time
They are used to generate hypotheses but are prone to bias and have no time reference
What are the advantages of cross sectional study?
Relatively cheap and quick
Provide data on prevalence at a single point in time
Large sample size
Good for surveillance and public health planning
What are the disadvantages of a cross sectional study?
Risk of reverse causality (don’t know whether outcome or exposure came first)
Cannot measure incidence (number of new cases)
Risk recall bias and non-response
case control study?
A type of analytical study
Retrospective
Takes people with a disease and matches them to people without the disease for age/sex/habitat/class etc
Study previous exposure to the agent in question
Quick and inexpensive
But retrospective nature shows only an association and data may not be reliable due to problems with patients’ memories
What are the advantages of a case-control study?
Good for rare outcomes (e.g. cancer)
Quicker than cohort of intervention studies (as the outcome has already happened – it’s retrospective)
Can investigate multiple exposures
What are the disadvantages of case-control studies?
Difficulties finding controls to match with cases
Prone to selection and information bias
What is a cohort study?
Prospective
Start with a population without the disease in question and study them over time to see if they are exposed to the agent in question and if they develop the disease in question or not
What are the advantages of a cohort study?
Possible to distinguish preceding causes from concurrent associated factors
Lower chance of selection and recall bias
Absolute, relative and attributable risks can be determined
Prospective - so can show causation where retrospective can’t
Good for common and multiple outcomes
What are the disadvantages of a cohort study?
Requires a control group to establish causation
Takes a long time
Loss to follow-up (people drop out)
Need a large sample size
What is a randomised control trial?
Patients are randomised into groups, one group is given an intervention and the other is given a placebo/control and the outcome is measured
Randomisation allows confounding factors to be equally distributed
Confounding and biases are minimalised
Lage, expensive, volunteer bias
Ethical issues – is it ethical to withhold a treatment that is strongly believed to be effective
Shows causation
What are the advantages of a RCT?
Low risk of bias and confounding
Can infer causality (gold standard)
What are the disadvantages of an RCT?
Time consuming
Expensive
Specific inclusion/exclusion criteria may mean the study population is different from typical patients (e.g. excluding very elderly people)
What are is the main issue with a controlled trial that is not randomised?
very subject to bias
Confounding factors are not equally spread across the groups
independent variable?
variable that can be altered in a study
dependant variable?
A variable that is dependant on the independant variables, or one that cannot be altered
What is meant by “odds” of an event and how is it calculated?
The odds of an event is the ratio of the probability of an occurrence compared to the probability of a non-occurrence
Odds = probability/ (1 – probability)
What is meant by odds ratio and how is it calculated?
The odds ratio is the ratio of offs for the exposed group to the odds for the non exposed groups
(P exposed/ (1- P exoposed)) / (P unexposed/ (1 – P unexposed))
Or can be interpreted as a relative risk when the event is rare
For case control studies it’s not possible to calcuate the relative risk, so the odds ratio is used
For X-sectional and cohort studies – both can be derived but odds ratio is used if it’s not clear which is the IV and which is the DV
epidemiology?
The study of frequency, distribution and determinants of disease and health related states in populations in order to prevent and control disease
Usual factors when measuring epidemiology of a disease – time, place, person (age, gender, class, ethnicity)