Data- Year 2

Question 1

Define the following:

• Incidence
• Prevalence
• Relative risk
• Epidemiology

Answer 1

Incidence: number of new cases of a disease in a population in a specified period of time

Prevalence: number of people in a population with a specific disease at a single point in time or in a defined period of time

Relative risk: measure of the strength of an association between suspected risk factor and the disease under study

Epidemiology: the branch of medicine which deals with the incidence, distribution, and possible control of diseases and other factors relating to health.

Question 2

What are the different sources of epidemiological data?

Answer 2

1. Mortality data
2. Hospital activity statistics
3. Reproductive health statistics
4. Cancer statistics
5. Accident statistics
6. General practice morbidity
7. Health and household surveys
8. Social security statistics
9. Drug misuse databases
10. Expenditure data from NHS

Question 3

Name the different type of studies?

Answer 3

• Descriptive study
• Analytical study
• Cohort study
• Trials

Question 4

What is a descriptive study?

Answer 4

• Describe amount and distribution of disease in a given population
• No definitive conclusions, does clue risk factors and aetiology
• Cheap, quick, overview

Question 5

What is an analytical study?

Answer 5

• Cross sectional (disease frequency/survey): observations in a point in time
• Case Control: comparison of 2 groups (cases/controls)
• Quick results
• In case controlled studies; two groups are compared; a group of individuals who have the disease (cases) of interest are identified and group of individuals who do not have the disease (controls)
• Data is gathered on each individual to determine whether or not they have been exposed to aetiological factor and average exposure is compared.

Question 6

What is a cohort study?

Answer 6

• Baseline data on a group, then followed until disease developed in sufficient numbers to allow analysis

Question 7

What is a trial?

Answer 7

• Test ideas about aetiology or evaluate interventions

- “Randomised controlled trial”: varying intervention on patients and analysis of results

Question 8

What are the different types of bais?

Answer 8

• Selection bias: sample is not representative of whole study population
• Information bias: Systematic errors in measuring exposure/disease e.g. researcher knowing “case”vs“control”, and working harder on “case”
• Follow up bias: one group of subjects is followed up more assiduously
• Systematic error: measurement bias where measurements tend to fall on one side of the truth e.g. machine calibrated incorrectly, poorly written survey

Question 9

Causality?

Answer 9

• Temporality: exposure comes before disease [only absolute criterion]
• Strength of association: relative risk ratio
• Consistency: repeated observation of association in differing populations
• Specificity: single exposure leads to single disease
• Biological gradient: dose response relationship i.e. exposure UP = risk UP
• Biological plausibility: association agrees with biology of disease
• Coherence: association does not conflict with biology of disease
• Analogy: another relationship exists that can be used as a model for current
• Experiment: suitably controlled experiment to prove association as causal(uncommon in human populations)

Question 10

What is the process of a clinical NHS audit?

Answer 10

• Identify problem or issue
• Set criteria and standards
• Observe practice/ data collection
• Compare performance with criteria and standards
• Implement change