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Flashcards in Tutorial 2: Use of Data Deck (38)
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Define disease.

Symptoms, signs – diagnosis. Bio-medical perspective.


Define illness.

Ideas, concerns, expectations – experience. Patients perspective.


List factors affecting uptake of care.

- Lay referral: going from family → community → traditional/cultural healing → medical system
- Sources of information: Peers, family, internet, TV etc.
- Medical factors: new symptoms, visible symptoms, increasing severity, duration.
- Non-medical factors: crisis/psychological state, peer pressure (spouse/friends), ICE, social class, economic, environmental, cultural, ethnic, age, gender, media.
- Issues:
○ Patient believe self to be healthy: physically fit, doesn’t want to use tablets
○ Doctor: rationale behind performing additional investigations, educate self of concerns regarding patient's health


Patient has irregularly irregular pulse. Atrial fibrillation is suspected. What investigations would you perform to confirm diagnosis?

- ECG: shows absent P waves, irregularly irregular QRS complexes.
- Urea & electrolytes (problems with kidney function)
- Thyroid function tests (TFTS): rule out hyperthyroidism
- Full blood count (FBC): to rule out anaemia.
- Can also do echocardiogram (assess the structure and function of the heart and valves to rule out other heart-related problems); Holter monitor.


What are the three main aims of epidemiology?

1. Description: To describe the amount and distribution of disease in human populations.
2. 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.
3. 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.
Epidemiology compares groups (study population) to find: aetiological clues, scope of prevention, and identify high risk groups.


What is the difference between clinical medicine and epidemiology?

Clinical medicine deals with the individual patient, epidemiology deals with populations. Distinction important in order to formulate a hypothesis about disease and risk. Normally done by calculating ratio:
Numerator/Denominator = Events/Population at risk
This ratio converted into rate by expressing it in terms of a specified time period (eg, per year) and a notional 'at risk' population of 10n (eg, %; per 1000; per 100,000).


Define relative risk.

Measure of the strength of an association between a suspected risk factor and the disease under study.
Relative risk (RR) = incidence of disease in exposed group/incidence of disease in unexposed group.


What are the sources of epidemiological data?

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?

Having knowledge, skills, understanding & confidence to use health information in order to be active partner in care, and to navigate healthcare systems.


What is CHA2DS2-VASc score?

Clinical prediction rules for estimating the risk of (thromboembolic) stroke in patients with non-rheumatic atrial fibrillation (AF). Score is used to determine whether or not treatment is required with anticoagulation therapy or antiplatelet therapy.
High score = greater risk of stroke & vice versa.
Takes into account age, sex, and history of CHF, hypertension, diabetes, vascular disease, TIA/stroke/thromboembolism.


When prescribing warfarin what is needed to be taken into account?

Bleeding risk (use HAS-BLED score) vs long-term consequences of stroke.


Compare NOAC's with warfarin.

NOAC's do not require regular blood test monitoring like warfarin, this appeals to most patients.
However, they are more expensive, and are not easily reversed like warfarin (vitamin K used) in case of bleeding.


What are SIGN guidelines and what are they intended for?

The guidelines are based on a systematic review of the scientific literature and are aimed at aiding the translation of new knowledge into action. The guidelines are intended to:
- Help understand medical evidence and use it to make decisions about healthcare.
- Reduce variations in practice and ensure patients get the best care available, no matter where they live.
- Improve healthcare by focusing on patient-important outcomes.
SIGN guidelines also provide rated evidence.


List types of studies.

Descriptive studies.
Analytic studies: Cross-sectional studies, Case control studies, Cohort studies.
Trials: randomised controlled trial.


Define descriptive studies and give limitations and advantages.

Describe the amount and distribution of a disease in a given population. Follow the time, place, person framework.
Does not provide definitive conclusion about disease causation but can provide insight about possible risk factors and aetiologies.
Cheap, quick and give a valuable initial overview of a problem.


What are descriptive studies useful in?

- Identifying emerging public health problems through monitoring and surveillance of disease patterns.
- Signalling the presence of effects worthy of further investigation.
- Assessing the effectiveness of measures of prevention and control (eg, screening programmes).
- Assessing needs for health services and service planning.
- Generating hypotheses about disease aetiology.


What are cross-sectional studies? Comment on advantages & disadvantages.

Observational study design (observations are made at a single point in time). Outcome and the exposures are measured in the study participants at the same time. Conclusions are drawn about the relationship between diseases (or other health-related characteristics) and other variables of interest
Used for population-based surveys, estimating prevalence in studies, calculating odds ratio, and disease frequency.
Advantages: Can be done quickly, inexpensive, and can be used to plan cohort studies.
Disadvantages: cannot infer causation as 1-time measurement performed, and can be biased.


Define case-control studies. Results from the study are expressed as what?

Two groups of people are compared: a group of individuals who have the disease of interest are identified (cases), and a group of individuals who do not have the disease (controls).
Data gathered about exposure to aetiological factor of interest. Average exposure compared to identify significant differences, and any factors that elevate or reduce risk of the disease.
Results expressed as odds ratio, relative risk or p values.


Define cohort studies.

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. Original group divided into subgroups based on exposure initially and then these groups are compared.
Results expressed as relative risks, with confidence intervals or p values.


What are advantages or limitations of cohort studies?

Advantages: Cohort studies allow the calculation of cumulative incidence, allowing for differences in follow up time.
Limitations: costly, and greater chance of losing subjects to follow-up based on the long time period over which cohorts are typically followed.


Define trials.

Trials are experiments used to test ideas about aetiology or to evaluate interventions. The “randomised controlled trial” is the definitive method of assessing any new treatment in medicine.
Two groups at risk of developing disease are taken. One is the intervention group from which causative factor is removed/neutralised. No alteration is made to 2nd control group. Data collected from both groups are relative risk is calculated. The aim is to determine whether modification of the factor (removing, reducing or increasing exposure) alters the incidence of the disease.
In a trial of a new treatment, the underlying design is the same: the intervention group receive the new therapy, the control group receive the current standard therapy (or a placebo) and the treatment outcomes (eg, reduction in symptoms) are compared in the two groups.


What factors are needed to be considered while interpreting results?

1. Standardisation
2. Standardised mortality ratio
3. Quality of Data: ensure data is trustworthy.
4. Case definition
5. Coding and classification
6. Ascertainment


Define standardisation.

A set of techniques used to remove (or adjust for) the effects of differences in age or other confounding variables, when comparing two or more populations.


Define standardised mortality ratio.

Standardised death rate converted to ratio, e.g. standard is 100, 120 means 20% more death than expected.


What is the purpose of case definition?

To decide whether an individual has the condition of interest or not. 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.


What is the importance of coding and classification?

Important to know what the rules are for converting clinical information into a code while storing data (e.g. death certificates). Sometimes when rules change it appears that a disease has become more common, or less common, when in fact it has just been coded under a new heading.


Define ascertainment.

Completeness of data. Higher incidence rates might be due to one country looking for it harder than the other one so making sure data is complete from each country will allow for better comparison if needed e.g. COVID-19 was tested more in South Korea so appeared to have higher cases as oppose to other countries who didn't test as much.


Define bias.

Bias is 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 different types of biases.

Selection Bias
Information Bias
Follow up Bias
Systematic Error
Publication bias


Define selection bias.

Occurs when the study sample is not truly representative of the whole study population about which conclusions are to be drawn. For example, 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.