The Use of Data - FoPC 2 Tutorial 2 Flashcards
What is General Practice the interface between? (2)
The public and secondary care
What percenatge of the population consult their GP? (1)
20%
What percenatge of the population are given referrals to secondary care? (1)
3%
What percentage of people ignore their symptoms? (1)
19%
What percentage of people treated their issues withoit medical advice or w/self medication? (1)
56%
Is the progression through levels of medical care related to the severity of disease (2)
Sort of, most patients who look after themselves tend to have self-limiting illnesses while those with more lifethreatening illnesses are in hospital. Not entirely true as severity of illness doesnt indicate severity of disease
Define Disease (using FoPC buzzwords)
Symptoms/signs leading to a diagnosis (biomedical persepctive of disease)
Define Illness (using FoPC buzzwords)
Ideas, concerns, expectations -> patients experience/perspective of
Example of a disease without an illness (1)
Hypertention
What issue may have to be considered when treating a disease without an illness?
Non-compliance (patient feels no different and stops taking meds for hypertentention)
What factors affect the uptake of care (no detail, just list - 4)?
Concept of lay referral Sources of info about healthcare Medical Non-medical factors
What is the concept of lay referral?
Granny knows best (because why should FoPC use plain english)
What sources of informtion might affect patients uptake of care? (8)
Peers Family Internet TV Healthpages in magazines and newspapers “What should I do?” booklet SHOW website Practice leaflet/website
What medical factors affect patients uptake of care? (4)
New symptoms Visible symptoms Increasing severity Duration
What non-medical factors affect patients uptake of care? (13)
Crisis Peer Pressure “wife sent me” Patient beliefs Expectations Social class (FoPC yr 1) Economic Pyschological Environmental Cultural Ethnic Age Gender Media
What are the three main aims of Epidemiology? (3 + detail)
Description - To describe the amount and distribution of disease in human populations. Explanation - To elucidate the natural history and identify aetiological factors for disease usually by combining epidemiological data with data from other disciplines such as biochemistry, occupational health and genetics. Disease control - To provide the basis on which preventive measures, public health practices and therapeutic strategies can be developed, implemented, monitored and evaluated for the purposes of disease control.
Why does epidemiology involve comparing groups? (3)
to detect differences that point to: - Aetiological clues (what causes the problem) - Scope for prevention - Identification of high risk or priority groups in society
What is compared in epidemiology?
You compare how often an event appears in one group with another similar group - may be defined by age/sex/location or even the same group over time
What is the difference between clinical medicine and epidemiology?
Clinical medicine dealths with individual patients while epidemiology deals with populations
Define “Incidence”
The number of new cases of a disease in a population in a specified period of time.
What does incidence tell us?
Incidence tells us something about trends in causation and the aetiology of disease.
Define “Prevalence”
The number of people in a population with a specific disease at a single point in time or in a defined period of time.
What does prevalence tell us?
Prevalence tells us something about the amount of disease in a population. It is useful in assessing the workload for the health service but is less useful in studying the causes of disease.
Can you have lifetime prevelance?
Yes It just depends on the number of people developing a disease, dying from it or recovering from it
Define “Relative risk”
The measure of the strength of an association between a suspected risk factor and the disease under study
What is the “equation” used to calculate relative risk
‘Incidence of disease in exposed group’ divided by ‘Incidence of disease in unexposed group’
Name some sources of epidemiological data (12)
Mortality data Hospital and clinical activity statistics Reproductive health statistics Infectious disease statistics Cancer statistics Accident statistics General practice morbidity statistics Health and household surveys Labour force surveys Social security statistics Drug misuse databases Expenditure data from NHS
What is health literacy?
Health literacy is about people having the knowledge, skills, understanding and confidence to use health information, to be active partners in their care, and to navigate health and social care systems.
What are NOACs (this is FoPC not cardio remember)? (3)
Newer drugs that dont require regular blood tests They are relatively inexpensive They are not easily reversed in the event of bleeding
List the 2 main study types
Descriptive Analytical
What does a Descriptive study attempt to do?
They attempt to describe the amount and distribtution of a disease in a given population for the purposes of gaining insight into the aetiology of the condition or for planning health services to meet clinical need
What might descriprive studies look at?
Disease alone or they also examine one or more factors (Exposures) that might be linked to the aetiololgy
What framework do descriptive studies follow?
Time, Place and Person framework
When are descriptive epidemiological studies useful?
Identifying emerging public health problems through monitoring and surveillance of disease patterns Signalling
When are descriptive epidemiological studies useful? (4)
Identifying emerging public health problems through monitoring and surveillance of disease patterns Signalling presence of effects worthy of further investigation Assessing needs for health services and sevice planning Generating Hypotheses about disease aetiology
List the types of Analytical studies (3 Cs)
Cross-sectional Cohort Case control
What is a Cross-sectional study? (3)
Disease frequency, Survery and Prevalence study
What happens in a cross sectional study? (2)
Observations are made at a single point in time Conclusions are drawn about the relationship between diseases (or health-related characteristics) and other variables of interest in a defined population
What is an advantage of using then crossectional study method?
It produces results quickly
What is a disadvantage to crossectional studies?
They are impossible to infer causations from
What happens in a case control study?
two groups of people are compared - those with the disease of interest and those without the disease data is then gathered in each individualto determine whether they have been exposed to the suspected aetiological factor The average exposure in the two groups is then compared to identify significant differences and give clues to factors which elevate risk of the disease under investigation.
Define ‘Cases’ in a case controlled study
A group individuals with the disease of interest
Define ‘controls’ in a case controlled study
A group of individuals who do not have the disease
What happens in a Cohort study?
Baseline data on exposure are collected from a group of people who do not have the disease under study. The group is then followed through time until a sufficient number have developed the disease to allow analysis. The original group is separated into subgroups according to original exposure status and these subgroups are compared to determine the incidence of disease according to exposure.
What do cohort studies allow?
They allow for the calculation of cumulative incidence, allowing for differences in follow up time
Define a ‘trial’ (in relationto epedimiology)
Trials are experiments used to test ideas about aetiology or to evaluate interventions.
What is the definitive methof of assessing new treatments?
Randomised controlled trial
What does a randomised controlled trial involve?
Two groups at risk of developing a disease are assembled, a study (intervention) group and a control group. An alteration is made to the intervention group (eg, a suspected causative factor is removed or neutralised), whilst no alteration is made to the control group. Data on subsequent outcomes (eg, disease incidence) are collected in the same way from both groups, and the relative risk is calculated.
What is the aim of a randomised controlled trial?
The aim is to determine whether modification of the factor (removing, reducing or increasing exposure) alters the incidence of the disease)
What factors must be considered when interpreting results? ()
Standardisation Standardised Mortality Ratio Quality of Data Case Deifinition Coding and Classification Ascertainment
Explain ‘Standardisation’
A set of techniques used to remove (or adjust for) the effects of differences in age or other confounding variables (sex, social class etc.), when comparing two or more populations
Explain the ‘Standardised Mortality Ratio (SMR)’
A standardised death rate converted into a ratio for easy comparison
Why is the quality of data important?
We have to ensure the data we use is trustworthy
What is the purpose of a case definition?
Its purpose is to deciden whether an individual has the condtiion of interest or not.
Why is the case deifintion important?
It is important in because not all doctors or investigators mean the same thing when they use medical terms. Differences in incidence of disease over time or in different populations may be artefact, due to differences in case definition, rather than differences in true incidence.
Why are fixed rules relating to classification and coding important?
Rules are drawn up to dictate how clinical information is converted to a code. They ensure information is accurate. If these rules change, it sometimes appears that a disease has become more common, or less common, when in fact it has just been coded under a new heading.
Define ‘Bias’
Any trend in the collection, analysis, interpretation, publication or review of data that can lead to conclusions that are systematically different from the truth.
List the 5 important types of bias
Selection Bias Information Bias Follow up Bias Systematic Error Publication bias
When does selection bias occur?
When the study sample is not truly representative of the whole study population about which conclusions are to be drawn
Give an example that illustrates selection bias
In a randomised controlled trial of a new drug, subjects should be allocated to the intervention (study) group and control group using a random method. If certain types of people (eg, older, more ill) were deliberately allocated to one of these groups then the results of the trial would reflect these differences, not just the effect of the drug.
Where does information bias arise?
Arises from systematic errors in measuring exposure or disease
Give an example that illustrates information bias
In a case control study, a researcher who was aware of whether the patient being interviewed was a ‘case’ or a ‘control’ might encourage cases more than controls to think hard about past exposures to the factors of interest. Any differences in exposure would then reflect the enthusiasm of the researcher as well as any true difference in exposure between the two groups.
When does ‘Follow up bias’ arise?
When one group of subjects is followed up more assiduously than another to measure disease incidence or other relevant outcome.
Give an example that illustrates ‘Follow up bias’
In cohort studies, subjects sometimes move address or fail to reply to questionnaires sent out by the researchers. If greater attempts are made to trace these missing subjects from the group with greater initial exposure to a factor of interest than from the group with less exposure, the resulting relative risk would be based on a (relative) underestimate of the incidence in the less exposed group compared with the more exposed group.
What is a ‘Systematic error’?
A form of measurement bias where there is a tendency for measurements to always fall on one side of the true value.
Why may a systemic error occur?
It may be because the instrument (eg, a blood pressure machine) is calibrated wrongly, or because of the way a person uses an instrument.
Where might systematic errors occur? (3)
Interviews Questionnaires Medical instruments
When does ‘Publication Bias’ occur?
Occurs where positive results have a greater chance of being published (even if the quality of the study is poorer than a similar study showing negative results)
Define ‘Confounding Factors’
One which is associated independently with both the disease and with the exposure under investigation and so distorts the relationship between the exposure and disease In some cases the confounding factor may be the true causal factor, and not the exposure that is under consideration
List three common confounding factors
Age Sex Social class
Explain 5 ways confoudnig factors can be managed
In trials, the process of randomisation (in effect the play of chance leads to similar proportions of subjects with particular confounding in the intervention and control groups). Restriction of eligibility criteria to only certain kinds of study subjects . Subjects in different groups can be matched for likely confounding factors. Results can be stratified according to confounding factors. Results can be adjusted (using multivariate analysis techniques) to take account of suspected confounding factors.
List the 9 criteria for causality
Strength of association Consistency Specificity Temporality Biological gradient Biological plausibility Coherence Analogy Experiment
Define ‘Consistency’
Repeated observation of an association in different populations under different circumstances.
Explain what is meant by ‘Temporality’
The exposure comes before the disease.
How is strength of association measured?
Relative risk or odds ratio
What term describes “a single exposure leading to a single disease”?
Specificity
Explain what is meant by ‘Biological gradient’
Dose-response relationship. As the exposure increases so does the risk of disease.
Explain what is meant by ‘Biological plausibility’
The association agrees with what is known about the biology of the disease.
Explain what is meant by ‘Coherence’
The association does not conflict with what is known about the biology of the disease.
What does ‘analogy’ mean?
Another exposure-disease relationship exists which can act as a model for the one under investigation. For example, it is known that certain drugs can cross the placenta and cause birth defects - it might be possible for viruses to do the same.
How can the audit criteria and standards to measure be set? (2)
Could define own Could utilise others if available
What are the disadvantages of defining your own audit criteria and standards? (2)
Time consuming Needs more research
What is the advantage of using others audit criteria and standards? (1)
Guidelines are based on systematic review of evidence
