Epidemiology Flashcards
What is epidemiology?
The study of the distribution and determinants of health-relates states or events in specified populations and the application of this study in the control of health problems
What is the most concise definition of epidemiology?
How often diseases occur in different groups of people and why
What are the 3 main types of disease prevention?
Primary
Secondary
Tertiary
What is primary prevention of disease?
The prevention of disease through the control of exposure to risk factors I.E reducing salt in your diet to reduce risk of developing hypertension
What is secondary prevention of disease?
The application of available measures to detect early departures from health and to introduce appropriate treatment and interventions - controlling hypertension with antihypertensive drugs to progression
What is tertiary prevention of disease?
The application of measures to reduce or eliminate long-term impairments and disabilities. minimising suffering caused by existing departures from good health and to promote the patients adjustments to their condition
Rehabilitation is an example of what type of intervention?
Tertiary
What is primary prevention in regards to the onset of disease?
Before the onset of disease
What is secondary prevention?
Slows progression
What is tertiary prevention?
Enables return functioning after insult
Define exposure in epidemiological terms?
Variable that we are trying to associate with a change in health status i.e. a drug, behaviour or ethnicity
What is outcome in epidemiology?
Defined disease, state of health, health-related event or death
Describe the birth and death rate in a stage 1 country?
High for both
Describe the natural increase in a stage 1 country
Stable or slow increase
Describe the natural increase in a stage 2 country
Very rapid increase
Describe the birth rate in a stage 2 country
High
Describe the death rate in a stage 2 country
Falls rapidly
Describe the birth rate in a stage 3 country
Falling
Describe the natural increase in a stage 3 country
Increase sows down
What happens to do the natural increase in a stage 4 country?
Falling and then stable
What is associated in stage 1 on the DTM?
Pestilence and famine
What is associated in stage 2 on the DTM?
Receding pandemics and crude death rate
What is associated in the late demographic transition?
Degenerative and man-made diseases
What is associated with the post-stage of demographic transition?
Delated degenerative diseases and emerging infections
What is pestilence and famine?
High birth rate and mortality and life expectancy at birth
There is urbanisation to which there is constrains on food supply - life expectancy is low at birth
What is receding pandemics?
A period of high birth rates and reducing mortality, vaccination emerges and the life expectancy increases
Agricultural development improves nutrition
What are degenerative and man-made diseases?
Addiction and obesity arises, lifestyle factors and non-communicable diseases predominate
Cancer and CVD - technology reduces the need for physical labour
Addiction, violence and other issues emerge
What are delayed degenerative diseases and emerging infections?
Country inequalities; emerging zoonotic infections
Health technology defers morbidity, albeit at increasing financial cost - inequalities within and between countries come to the forefront.
What affects population pyramids such as the UAE causing a massive bulge?
The immigration of young males looking for work
What accounts for the population decline in 1918/1919?
Pandemic H1N1 Influenza
Is there a correlation between child mortality and income per captia?
There is a negative correlation
What was the first medication available for AIDS/HIV?
AZT
What treatment was available for mothers infected with AIDS-HIV?
ACTG 076 for mother and AZT for baby to decrease transmission chance
Which drug prevents transmission of AIDs-HIV between mother and child?
AZT
What AIDs-HIV therapy targeted retrovirus proteases?
highly active antiretroviral therapy (HAART)
What is the highest degree of evidence?
Systematic reviews and meta-analysis
What are the two types of epidemiological research?
Descriptive and analytical;
What is qualitative research?
- Explores underlying ideas and themes to inform research questions and possible future hypotheses
- Expresses its findings and outputs of qualitative research in words
- Relies on smaller numbers of participants, but goes in substantial detail
What are the 3 main building blocks of epidemiology?
What numbers and measures do we use?
• Measures of frequency and association
• Comparisons and adjusting for differences
Where do these measures come from?
• Descriptive epidemiology
• W and interventional study design
• Systematic reviews and meta-analysis
How do we interpret epidemiological findings
• Association, causation, validity and bias
• Confounding and effect modification
What is a DALY?
Disability Adjusted Life Years; The DALY is a measure of disease burden that combines years of life lost from ill-health, disability or premature death. Like any other epidemiological measure, it’s not perfect, but it tells us a story.
What are three main groups of conditions?
- Communicable disease
- Non communicable disease
- Injuries
What is the leading cause of death in the UK (2017)?
Ischemic heart disease
What is the leading cause of morbidity in the UK?
Back pain
What is the leading cause of mortality in the UK?
Road injury
Which modifiable behavioural risk accounted for the most deaths?
Drugs
What are the four discrete measures of frequency?
- Odds
- Prevalence
- Cumulative incidence
- Incidence rate
What are Odds?
The ratio of the probability (P) of an event to the probability of its complement (1-P)
Odds=Number of people with disease/ Number of people without
Define prevalence
The proportion of individuals in a population who have the disease or attribute of interest at a specific timepoint – a snapshot of the situation
What does prevalence show?
- the occurrence of disease
- duration of disease-especially when short
- Does not provide information of new cases of a disease
- Does not help in determining casual inference
- No units
What is the equation for prevalence?
Prevalence= Number of people with the disease/Total number of individuals of population
Define cumulative incidence
The proportion of the population with a new event during a given time period
Cumulative incidence = Number of new cases during the period of interest/Number of disease-free individuals at the start of this time period
What are the other names for cumulative incidence?
Risk
incidence proportion
What do we need to calculate cumulative incidence?
Follow up period, must be the same for all participants but not always possible
What is person time?
The time participants spend in the study, from entering study to diagnosis
What is incidence rate?
The number of new cases per unit of person time
Incidence rate= Number of new cases during the follow-up period/Total person-time by disease-free individuals
What is the definition of rate?
Definition of rate- can only be expressed as new cases per unit of person time – used inappropriately for measures that are risk
Your clinical director wants to understand what the likely year-on-year cost of a new drug is going to be, that will replace the need for traditional anti-hypertensive medicines, including in patients on existing anti-hypertensive therapies. Which epidemiological measure would be most useful?
Prevalence
Your Director of Public Health wants to undertake cost-effectiveness research into the value of influenza vaccines for persons over the age of 65 years. Using data taken from a select group of GP health records in England, which epidemiological measure would be most useful?
• Incidence -good for disease in short term period, better indicator of disease burden than prevalence – Cross sectional measurements underestimate
The Professor of Clinical Infection has conducted a 24-month study looking at the effectiveness of a new tri-valent influenza vaccine. All (100%) participants were followed up from day 1 to day 730 of the study. Which outcome measure would best approximate to the effectiveness of the vaccine in the cohort receiving the vaccination?
Cumulative incidence
What is standardisation?
Standardisation- look at the difference in incidence such Population, demographic and access to health care
What is define direct standardisation?
Comparable incidence: a type of adjustment that allows compare like-for-like between populations
• this gives a similar incidence - eg. 120 strokes per 100k/yr
What is indirect standardisation?
Requires that you know a benchmark measure – such as national incidence rate – in order to conduct the standardisation by applying the national age-specific incidence against the age structure of the institution or geography of interest.
• this gives a ratio out of 100 (or sometimes 1.0)
How is direct age standardisation done?
specific incidence to standard population is worked out using European standard population
What is crude rate?
Crude rate= Incidence/Population x 100k(per pop figure)
How do you calculate expected cases?
Rate x Standard Population x 100,000
What is age standardised incidence?
A summary measure of the rate that a population would have if it had a standard age structure
Define crude incidence rate
A crude incidence rate is the number of new cancers of a specific site/type occurring in a specified population during a year, usually expressed as the number of cancers per 100,000 population at risk
How is indirect standardisation done?
- We work out a expected count from looking at national figures(per 10k) comparing it locally.
- Used when we have high level data outcomes but cant make direct comparison
- Granular=patient data
- Aggregated data=top level outcomes
What are the three main reasons for variation?
Unwarranted variation
Explained variation
Statistical artefact
What is unwarranted variation?
Refers to medical practice pattern variation that cannot be explained by illness, medical need or the dictates of evidence based medicine
Define statistical artefact
An inference that results from bias in the collection or manipulation of data. The implication is that the findings do not reflect the real world but are an unintended consequence of measurement error
What is national mortality presented as?
Per 10,000 procedures
What is the SMR?
Dividing the observed count by the expected count
Standardised mortality ratio
Where is SMR used?
SMR < 75, as a marker for healthy life expectancy or premature death
What are granular and aggregated data?
Lowest level data in dataset (granular); data combined from several measurements (aggregate)
What is SHMI?
Summary hospital level mortality indicator uses the process of indirect standardisation to produce ‘expected’ number of deaths by a series of adjustments taking into account the volume of cases
How is SHMI presented?
Using a funnel plot
What type of standardisation is used in SHMI?
Indirect standardisation
What is count?
That is the number of referrals
What is rate?
The number of referrals divided by head of population
What is standardised incidence ratio?
The difference between observed and expected values
What is descriptive epidemiology?
Describes the problem often at an aggregated level ; can be used to inform later analytic research
What are the examples of descriptive epidemiology?
Case report Case series Cross-sectional Longitudinal ecological
What is analytic epidemiology?
Deploy and test hypotheses, often at a person level through which association can be measured and causation inferred.
Which type of epidemiology is used for hypothesis testing?
Analytic
What are the examples of analytic epidemiology?
Observational Cross sectional Ecological Case control Cohort studies
What are the main concepts for descriptive epidemiology?
Person (Demography, age, gender and status)
Place
Time (over a specified period)
What is exposure?
Age, gender and occupation would be considered exposures; as would living in a certain area
What are outcomes?
Often times focused on morbidity and mortality
What are the typical measures?
Incidence and prevalence Often point estimates with a confidence interval around them
What is a statistic?
A fixed value, derived from a sample that estimates the value in a population
What is a parameter?
A fixed, often unknown value, which describes an entire population
What is a point estimate?
Point estimation involves the use of sample data to calculate a single value which is to serve as a “best guess” or “best estimate” of an unknown population parameter. A statistic that seeks to estimate the parameter
What are case reports and case series used for in medicine?
Often these are used to communicate new diseases, new presentations or new findings
Today they’re often about unusual findings and can be structures as a bulletin or as a learning opportunity so called Continuing Medical Education or in the UK Continuing Professional Development – CME and CPD
What is a cross sectional study?
- Typically describes the prevalence of a condition across a population at a single point in time: a snapshot at a single point in time
- A survey is an example of a cross-sectional study
- Useful in circumstances where you may not have the money or time to undertake a study in detail
- Lacks follow up so risk or temporal relationships cannot be easily determined
Why can’t temporal relationships be established in a cross-sectional study?
There is a lack of follow up
What are the advantages of a cross-sectional study ?
Where you may not have the money or time to undertake a study in detail
What is an example of a cross-sectional study?
Survey
What is ‘benchmarking’?
Taking the point estimate in our population and compare it to a similar area as a single point estimate of disease
What are longitudinal studies?
- Descriptive longitudinal studies describe the prevalence/incidence of an exposure or outcome over time
- It may be made up of more than one cross-sectional analysis (aggregated data)
- Alternatively it may look to follow the same participants over time (person-level data)
- The term longitudinal is quite often loosely applied to any study – descriptive or analytic that involves management
What is person-level data?
Follow the same participants over time
What is an ecological study?
Compare groups aggregated data
Which type of epidemiology is used in public health care practice?
Descriptive
What type of epidemiology is used more in research settings?
Analytic
What type of epidemiology provides estimates of morbidity such as prevalence or incidence rate?
Descriptive
What is the correct interpretation of a confidence interval?
The range of values within which we are 95% confident the true value lies.
The confidence interval is typically inversely proportional to the number of observations
What is the typical relationship between the confidence interval and the number of observations?
Inverse relationship
What are ecological studies?
Unit of observation is the group-only aggregate level data, such as occupation, place or timing
Ecological studies are studies of risk-modifying factors on health or other outcomes based on populations defined either geographically or temporally. Both risk-modifying factors and outcomes are averaged for the populations in each geographical or temporal unit and then compared using standard statistical methods
What is the core principal of ecological studies?
Focuses on the comparison of groups rather than individuals
What is ecological fallacy/aggregation bias?
A formal fallacy in the interpretation of statistical data that occurs when inferences about the nature of individuals are deduced from inferences about the group to which those individuals belong.- we need individual level data to prove it from ecological studies
What are the advantages of ecological studies?
- First step in hypothesis generation
- Use secondary data sources that are already available therefore inexpensive/quick to complete
- Useful when the variability of exposure within each group is limited
What are the disadvantages of ecological studies?
- Always subject to ecological fallacy
- Relies on secondary data collected for different purposes which may not be compatible between countries or time periods;
- Unclear whether the exposure preceded the outcome
What types of data is used by ecological studies?
Secondary data
What is primary data?
Primary data are those that are collected by the researcher first-hand. Primary data are fantastic because they will have been collected for a pre-specified purpose: to test the hypotheses or answer the research question(s) set by the researcher. But of course, this comes at significant cost – both financial and in terms of time. Collecting data (and cleaning it) is a hugely time-consuming process and will often take a very large proportion of an overall research project’s duration and budget.
What are the disadvantages of primary data?
Huge time consuming process and expensive
What is secondary data?
Secondary data is the term applied to data that have been collected for another purpose – and then potentially ‘recycled’ for a different purpose. Of course, the downside is that secondary data analyses may have to make a series of assumptions because the data analysed weren’t intended for the new purpose. This may in turn introduce critical limitations on how the findings of such a study are interpreted. But the upside, is that secondary data analyses are usually faster and cheaper to undertake.
What is the UK hospital administrative data set?
Hospital episode statistics
What is non-routinely collected data?
Non-routinely collected data are the corollary to primary data (as termed by academics). They include surveys and other bespoke datasets. In professional practice (outside research) non-routinely collected data are usually prohibitively expensive and time-consuming to operate, so their use is limited.
What is data linkage?
Data linkage is a process which temporarily brings together two or more sets of administrative or survey data from different organisations to produce a wealth of information which can be used for research and statistical purposes. This allows for the true value of the data to be realised
Why don’t we already data link?
- Technical issues: despite multiple attempts to join up health records, we’ve repeatedly failed as a health service to deliver the technological platform or solution necessary.
- Privacy concerns: there are very reasonable ethical questions and accompanying legal constraints on how we hold, exchange and analyse health information. However, most patients are surprised that health records are not routinely shared and express frustration at having to provide the same information repeatedly to multiple organisations that they regard as being the same NHS.
What do cross sectional studies allow?
Measure outcome and exposure at the same time in this snapshot without follow up
Assess the prevalence of a disease but not the incidence rate or risk due to a lack of followup period
What is the main limitation with cross-sectional studies?
No information regarding the temporal relationship between exposure and outcome can be collected so no causal associations can be found or know if exposure came before outcome
Surveys-common descriptive data
What is the most common method of data collection?
Questionnaires but could collect blood samples etc. as long as the data is only assessed once
What is observational data?
Involves the investigator observing the populations or individuals; they don’t interfere or manipulate the exposure in any way i.e. case control study
What is a case controlled study?
A case–control study is a type of observational study in which two existing groups differing in outcome are identified and compared on the basis of some supposed causal attribute
How are case controlled studies designed?
• Case definition-clear eligibility criteria are defined in picking our cases (eg age/gender)
How are controlled picked in a case control study?
• Picking controls- source of controls (eg from same study population as cases and representative of population at risk) and exposures should be measurable with similar accuracy to exposure in cases
What is recall bias?
Self reported recall of usual behaviour may not be comparable in cases and controls. For example if you have the disease in question you might have spent a long time trying to explain it – and therefore be more likely to recall an exposure.
What are the advantages with a case control study?
- Good for studying rare diseases
- Relatively inexpensive to conduct
- Quick to obtain data
What are the disadvantages of case control study?
- There may be bias associated with exposure assessment- in reporting
- Difficulty selecting control group – the ‘matching’ process
- Limited to assessing just one outcome
- Cannot provide information about temporal relationship between an exposure and disease
What is a cohort study?
Typically involves a group of people without disease who are observed over a period to see what happens to them – also known as a longitudinal study
What are the 2 main steps in a cohort study?
- Select target population and assess their exposure status
* Follow these people to check up if they develop the disease or outcome of interest
What is the defining characteristic of cohort studies?
They track people forward in time from exposure to outcome
How is the sample selected in a cohort study?
- If you want to study a chronic disease associated with ageing, you may want to restrict your target population
- The exposure of interest may be rare so may need to target a specific population
- Should initially attempt to identify as many subjects as possible without invoking any restrictions
How do you assemble a cohort?
- By geographic region
- By occupation
- Based on disease
- By risk group
- Birth cohort
Give 3 ways by which assessing exposures could be measured?
- Self-report
- Taking physical measurements
- Using existing records
Outline 4 ways by which you may ascertain outcomes?
- Routine surveillance
- Death certificates
- Medical records
- Directly from the participant
What is the relative risk?
Relative risk= incidence in the exposed/incidence in the unexposed
Eg if RR=3 , then 3 times as likely or 300% more likely
What are the two types of cohort studies?
Prospective cohort studies
Historical/retrospective cohort studies
What is a prospective cohort study?
• Prospective cohort study/cohort- identify a cohort and their exposure to measure outcomes
What are historical/retrospective studies?
• Historical cohort/retrospective cohort study- a group of individuals form the cohort, with a distribution of exposures and outcomes which are measured contemporaneously or extracted from health records. Historical cohort studies are typically lower quality than prospective cohort studies because there is a greater risk of both selection and information biases.
What are the two ways of assessing whether exposure is associated with outcome?
- Experimental studies
* Observational studies
What is the strength of a study?
Robustness of evidence
What is the gold standard of assessing whether exposures is associated with outcomes?
Clinical trials and experimental
What is the major limitation of observational study design?
The observed groups may differ in characteristics other than the variable of interest
What are randomised controlled trials?
Treatment compared to a control. The treatment is tested using clinical trials before. Ideally a placebo as the control
What is a placebo controlled trial?
Placebo for control so no active drug
What is the gold standard study design for evaluating an intervention of an outcome?
Randomised
What is intention to treat?
Intention to treat- Analysing patients according to which group they were originally assigned
Intention to treat analysis-Process of statistically analysing patients outcome using the original groups to which they were allocated irrespective of whether they took the medicine or not
What are the two steps of the randomisation control process?
- Generation of the allocation sequence
* Implementation of the allocation -allocation concealment
What is the allocation sequence?
- Simple randomisation-take out of hat and allocate alternating
- Good way-random numbers table or software , if the number is large enough then should be identical
What is allocation concealment?
Delivery could impact choice-eg give better drug to patients without comorbidities.
One method-sequentially numbered opaque envelopes- open in order not in advanced which are sealed- a case of seeing through light is bad. Example where it did not work -Eg Captopril Prevention Project (CAPP) trial comparing the effects of an ACE inhibitor and conventional therapy had the doctors opening the envelopes giving preferential drugs to participants
How many arms can a placebo-controlled double blinded trial have?
More than 2, such as different dosages
What is blinding?
Blinding- one or more parties are unaware of which treatment arm they have
• Prevent unconscious and convicted bias
• All parties are possible sources of bias- eg the patent, clinical staff in administration, physician assessing treatment and team interpreting results
• Single blind- participants
• Double blind-participant and staff
What does double blinding do?
preventing performance and detection bias
What is performance bias?
Systematic differences between group in care that is provided or in the exposures to factors other than the exposure of interest
What is detection bias?
Systematic differences between groups in how outcomes are determined- eg get more exams/test hence having a greater chance of outcome being positive
Why is blinding not possible sometimes?
Eg for surgeons/logistics, ethically cant blind, costly, more complicated and harder for drug titration.
Blinding helps improve internal validity
What determines the sample size?
1) The difference between groups
2) Study’s power
3) Study’s alpha
What happens to the sample size as the alpha increase?
The sample size increases
What is a type 1 error?
False positive (Alpha)
What is the p value?
the p-value is the probability of getting your results if actually there’s no real difference. That means it’s the probability of a false positive.
What is a type 2 error?
False negatives
How does alpha and power affect sample size?
A smaller alpha
Smaller beta (increases power)
Increases sample size
What is the relationship between beta and power?
As beta decreases, power increases
How do you mitigate the risk of losing people through follow up?
Include more people in the study
What is the major problem with observational studies?
Observed groups may differ in other characteristics including the observed characteristic
What is the gold standard for robust evidence clinicallY?
Clinical trials or experimental studies
What is random collection?
Means that all participants have an equal chance of assignment to each of the available interventions
Outline the potential sources of bias in a trial
- Patient being treated
- Clinical staff administering the treatment
- Physician assessing the treatment
- Team interpreting results in care that is provided or in exposure to factors other than the exposure of interest
What is the power of a study?
The power of a binary hypothesis test is the probability that the test rejects the null hypothesis when a specific alternative hypothesis is true — i.e., it indicates the probability of avoiding a type II error (Should be between 80-90%)
What would a 90% power demonstrate?
90% of the time you would get a statistically significant result. In 10% of the cases, your results would not be statistically significant
What are the two types of literature review?
Narrative and Systematic Reviews
What is a narrative review?
Brings together the published literature into a single article enabling the reader to rapidly understand the issues
Sometimes referred to as a literature review, scoping review or non-systematic review
What is a systematic review?
Sets out a highly structured approach to searching, sifting, including and summarising the literature
Often presented as the basis for meta-analysis but also exists separately
What are the strengths with a narrative review?
- Agile, normally easier and faster to write: may often be more up to date than the latest ‘Systematic Review’.
- Particularly useful when looking at areas with limited research or higher levels of variation in research approaches.
- Can be very useful where work from different disciplines is being brought together with a less easily answerable research question.
What are the limitations of a narrative review?
- the author is free to select works (sometimes that may support their opinion): although ethical authors and robust peer review should prevent overlyspeculative or unbalanced reviews.
- with no search being specified, it is possible that important evidence is omitted by chance (rather than intent).
What are the strengths of a systematic review?
- Aims to collate all available evidence that relates to a focused research question.
- Implements a highly specified protocol that enables reproducibility. This will usually involve a structured search.
- ‘Includes’ evidence based on prespecified criteria: inclusion criteria/exclusion
- Can take many months to design the search, review all sources (often thousands) and then synthesise the findings.
What are the limitations of a systematic review?
- Only as good as the method employed: a less-thancomprehensive search structure may not return all the evidence.
- Only as good as the indices searched.
- Only as good as the evidence that it incorporates.
- Very quickly out of date - often exacerbated by the delay in publishing. Look at the search date, not the publication date!
What should be used in a structured search?
Using key words, bullions and wildcards
What are the differences between indices and registries?
Indices are based on published research whilst registries are registration of research yet to be completed or published
Indices-eg from Ovid,Medline and others
What is publication bias?
Publication bias-prevents/precludes risk if we register early- not reporting negative findings and overly reporting positive findings
What flow diagram is used in designing a systematic review?
PRISMA diagram
What is grey literature?
The term grey literature refers to research that is either unpublished or has been published in non-commercial form. Examples of grey literature include government reports. policy statements and issues papers; grey literature provides information with varying degrees of accuracy
Not peer reviewed or necessarily searchable within PubMed
We access grey literature using open grey or google scholar
How can grey literature be accessed?
Open grey
Google scholar
What is the Cochrane Collaboration?
Seeks a world of improved health where decisions about health and healthcare are informed by high-quality, relevant and up-to-date synthesised research evidence
What is a meta analysis?
Meta-analysis is a quantitative, formal, epidemiological study design used to systematically assess the results of previous research to derive conclusions about that body of research. Typically, but not necessarily, the study is based on randomized, controlled clinical trials
What is a pooled estimate of association?
Adding the power each of these studies to create a better overall study
What do the horizontal lines on a forest plot illustrate?
The confidence interval of the study
What can be said with a study with a wider confidence interval?
The less reliable the results
What is the vertical line on a forest plot?
The line of no effect, the position at which there is no clear difference between the intervention group and the control group
What does weighting mean on a forest plot?
The amount of influence an individual study has had on the pooled result
What does I^2 <50% mean?
That the studies are considered homogenous
What type of effect model can be used for homogenous studies?
Fixed effect model
What type of effect model can be used for hetereogenous studies?
Random effect model
When the study I^2>50%, what does this suggest?
That the study is heterogeneous
What are the sources of heterogenity in meta-analysis?
Clinical: patients, selection criteria picking different types
Methodological: study design, blinding, intervention approach
Statistical: reporting differences
What are the two effects in regards to weighting of studies?
Fixed effect
Random effect
What is publication bias?
The type of bias that occurs in published academic research
Occurs when the outcome of an experiment or research study influences the decision whether to publish or otherwise distribute it
What does a publication funnel plot suggest?
A publication funnel plot can show the balance of evidence between studies assuming an overall effect size: more publications on one side of the line may suggest that some studies may not have been reported.
What are the limitations of meta-analysis?
- It can be limited by the quality of the studies included, the statistical methods employed and is often possible after multiple interventional/observational studies have been undertaken
- It always almost necessitates a systematic review to identify the papers/studies to be included in the estimates
- Sometimes it’s necessary to go back to the original authors of included studies to ask for more data enabling the meta-analysis to be conducted
What is conducted to establish the efficacy of interventions in the real world?
Real World Evidence
What is an endpoint?
An outcome that usually describes a clinically meaningful outcome
-Survival would be a measure of efficacy in therapy
What is the definition of efficacy?
how well a therapy works in achieving a desired outcome.
What is safety?
how well a therapy works in not causing adverse even
What are the two main types of efficacy end point?
Primary end-point
Secondary endpoint
What is a primary endpoint?
This is the endpoint for which the study has been powered; that is to say that the number of trial participants (sample size) will have been recruited on the basis of the pre-specified power and difference.
What is a secondary endpoint?
Secondary endpoint – it is common that a study will want to examine a slightly different endpoint in addition to the primary endpoint. For example, while a study seeks to examine survival another – often ‘softer’ - measure such as recurrence of disease or hospital admission might also be measured. If the secondary endpoint is proven but the primary endpoint is not, then the findings of the study may still contribute to the understanding of disease.
What is a safety endpoint?
- Safety endpoints are quite intuitive. On the one hand it could be anaphylaxis or direct mortality associated with the therapy. Such major issues should usually be detected early in the trial process (before its rolled out to large numbers of patients). But more commonly the safety endpoints will be more nuanced: potentially measuring commonly observed adverse events (AEs) and grading them into a hierarchy of significance. A large proportion of patients reporting AEs will require investigation.
- Eventually a judgment will need to be made as to what extent the safety profile (or lack thereof) of a therapy is offset by the efficacy.
What is a composite endpoint?
This is a variation of the above and could potentially describe any endpoint. The term composite simply means that multiple potential endpoints have been added together. This is particularly common when an outcome is uncommon. For example, one might combine myocardial infarction and ischemic stroke to give a new composite endpoint of ‘cardiovascular event’
