7 Observational Studies and Routine Data Flashcards
Q: What is the hierarchy of study design? (7)
A: Systematic reviews and meta-analyses (highest – but can still be inadequate)
Randomised Controlled Trials
Cohort studies
Case-control studies
Ecological studies
Descriptive/cross-sectional studies
Case report/series (lowest – but can still be valuable)”
Q: What are descriptive studies in epidemiology?
A: examine the distribution of disease across various factors including population or sub-groups, geographical location and time period
Q: Best study design to determine the accuracy of diagnostic tests?
A: cross- sectional design
Q: Best study design to determine disease prognosis.
A: cohort study
Q: Best study design to determine the causes and risk factors of a disease?
A: various non-randomised designs
Q: Best study design to determine population healthcare needs?
A: various, inc ecological (aggregate) studies
Q: Best study design to determine treatment efficiency.
A: randomised trial
Q: What data is used in descriptive studies? (3) Where does data come from for other study designs?
A: Types of data used are:
Routine e.g. births, deaths
Survey e.g. Health Survey for England
Performance management: Quality and Outcomes Framework for GPs
Other study designs tend to collect their own data
Q: List 3 cross sectional survey examples.
A: • 2001 Census
• Health Survey for England
• NHS Inpatient Survey on patient experience
Q: What is routine data?
A: Data that are routinely collected and recorded in an ongoing systematic way, often for administrative or statutory purposes and without any specific research question in mind at the time of collection
Q: What are the types of routine data? (8)
A: Health outcome data* e.g. deaths, hospital admissions and primary care consultations or prescriptions, levels of well-being from national surveys
Exposures and health determinant data, e.g. smoking, air pollution, crime statistics
Disease prevention data, e.g. screening and immunisation uptake
Demographic data, e.g. census population counts
Geographical data*, e.g. health authority boundaries, location of GP practices
Health service provision data e.g. bed staff counts
Births
Deaths
Q: What are the advantages of routine data? Cost? Availability? Collection procedure? (4)
A: Relatively cheap Already collected and available Standardised collection procedures Relatively comprehensive – population coverage, large numbers Wide range of recorded items Available for past years Experience in use and interpretation
Q: What are the disadvantages of routine data? (5)
A: May not answer the question (no information or not enough detail)
Incomplete ascertainment (not every case captured)
Variable quality (e.g. variable diagnosis fields) // Validity may be variable (i.e. do they measure what you think they measure?)
Disease labelling may vary over time or by area
Need careful interpretation
Q: What are examples of health outcome data? (8)
A: Mortality Cancer Notification of infectious diseases Terminations of pregnancy Congenital anomalies Hospital episode statistics GP data e.g. QOF (Quality of Outcomes Framework) Road Traffic Accidents
Q: Why are cross sectional studies useful? What do they describe? Downfall?
A: useful for health care providers to allocate resources efficiently and plan effective prevention
Describe status of individuals with respect to absence or presence of both exposure and disease assessed at the same point in time
but cannot easily distinguish whether exposure preceded disease: chicken or egg
Q: What are cancer registrations? Useful for? Linked to? Good data?
A: Voluntary notification to local cancer registry: now national system (Also from death certificates)
both incidence and survival information
Increasingly being linked to hospital admissions data and national clinical audits
Good epidemiological data- allows us to determine most common types of cancer
Q: Who reports infectious diseases? Examples of such diseases. (4)
A: doctors
Includes food poisoning, meningitis, tuberculosis and plague
Q: What is the quality and outcomes framework (QOF) a component of? Rewards? Collection? Published?
A: component of the new General Medical Services contract for GPs from April 2004
rewards practices for the provision of quality care, and helps to fund further improvements in the delivery of clinical care
Collected in a national database system: Quality Management Analysis System
Practice-level data are published; being phased out in many areas
Q: What is the finished consultant episode?
A: the time spent under the continuous care of a specific consultant
Q: What is admission?
A: A patient’s stay in hospital, so comprises 1+ episodes and/or transfers between hospitals
Q: Why are case controls studies good? Suitable for? Requires? What’s compared?
A: Relatively cheap and quick to conduct
studying what might cause rare diseases
cases (with disease) and controls (without disease) and compare those who are exposed and unexposed from each group
You are comparing odd of being exposed among cases and controls
Q: What are controls in a case control study? Should be?
A: subjects free of the disease (or outcome of interest) during the same period of time in which the cases were identified
representative of the population of individuals who would have been identified and included as cases if they had also developed the disease
Q: What is the most difficult and critical issue in the design of case-control studies?
A: Selection of an appropriate comparison group
Q: What are sources of controls? (3) (general population) What do they all vary in? (4)
A: Neighbourhood
Friends/relatives (depends on disease)
Hospital or clinic-based
These all vary in amount of recall bias (getting people to remember things about the past), response rates, selection bias, cost
Q: What are the advantages of case control studies? (3)
A: Good for rare diseases
Quick and cost-efficient
Can investigate many exposures simultaneously
Q: What are disadvantages of case control studies? (5)
A: Problems of selection of controls (Selection bias)
Subject to recall bias
Uncertainty of exposure- disease time relationship
Poor for rare exposures
Cannot calculate incidence rates directly (usually fixed number of controls in sample)
Q: What is a cohort? eg? What does it represent?
A: “cohort” is a group of people who have something in common:
– All patients registered with the same GP
A cohort represents the outcome-free population from which cases (people with the outcome) eventually arise
Q: What does a prospective study compare? Looks at? Speed?
A: – Compare rates of disease in the exposed group and unexposed groups.
– Thus, looking at outcome after some time has passed
slower than retrospective
Q: What is a retrospective study usually conducted with? Looks at? Speed?
A: – Done with routine data usually.
– Use data to look at the relationship between exposure and outcome.
– Quicker way of doing cohort study– Can collect whatever data you like but have to wait a few years to have enough data
Q: What are the advantages of cohort studies? (5)
A: Able to look at multiple outcomes
Able to follow through the natural history of disease
Good design to look at risks related to rare exposures
Incidence can be calculated
Can minimise bias in estimating exposure if prospective
Q: What are the disadvantages of cohort studies? (4)
A: Inefficient for studying rare diseases
Expensive and time consuming (if prospective)
Loss to follow-up may introduce bias
Healthy worker/volunteer effect
Q: What does the standardised mortality ratio represent?
A: It represents the ratio of the number of observed deaths (or cases of disease) (O) in a particular population to the number that would be expected (E), if that population had the same mortality or morbidity experience as a standard population, corrected for differences in age (and sex) structure.
Key confounders such as age may vary between populations. Population death rates may be compared taking into account (or “adjusting”) for the effect of age
Q: How is the standardised mortality ratio calculated?
A: number of observed deaths
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number of expected deaths if experienced the same age specific rates as standard population