The Use of Data

Question 1

What percentage of people with an illness at any given time go to the doctors? And how many of them are referred?

Answer 1

20% go to doctors

3% of them get referred

Question 2

What is disease?

Answer 2

Bio-medical perspective of symptoms and signs ultimately leading to a diagnosis

Question 3

What is illness?

Answer 3

The patient’s perspective of their disease and the way it affects them

Question 4

What factors affect uptake of case

Answer 4

Sources of information - peers, family, internet, TV
Medical factors - new symptoms, increasing severity, duration
Non-medical factors - peer pressure, beliefs, expectations, cultural

Question 5

List some sources of epidemiological data

Answer 5

Mortality data
Hospital activity stats
Reproductive health stats
Cancer stats
Accident stats
Drug misuse databases
Expenditure reports from the NHS

Question 6

What are SIGN guidelines?

Answer 6

There to:

Help healthcare professions and patients understand medical evidence and use it to make informed decisions

Reduce unwarranted variations in practice

Improve healthcare

Question 7

What are descriptive studies?

Answer 7

Attempt to describe the amount and distribution of a disease in a given population.

Does not provide definitive solutions about causation

Question 8

What are the benefits and drawbacks of descriptive studies?

Answer 8

Benefits - quick and cheap

Drawbacks - Do not provide definitive solutions about causation of a disease (can however give clues about possible aetiologies and risk factors)

Question 9

What are the three types of analytic studies?

Answer 9

Cross-sectional, case control and cohort studies

Question 10

What are cross-sectional studies?

Answer 10

Observations made from a single point in time and show disease frequency/survey or prevalence

Question 11

What are case controlled studies?

Answer 11

Two groups of people are compared; a group that have the disease (cases) and a group who don’t (controls)

Question 12

What are cohort studies?

Answer 12

Baseline data on exposure is collected from a group that does not have the disease under study and then this data is compared to a group of people who do have the disease to allow analysis

Question 13

What are trials?

Answer 13

Experiments used to test the ideas about aetiology or to evaluate interventions

Question 14

What type of trial is the definitive method for assessing any new treatment in medicine?

Answer 14

Randomised controlled trial

Question 15

What factors are there to consider in the interpretation of data from trials?

Answer 15

• Standardisation (statistical technique to remove differences in age or other confounding factors e.g. standardised mortality ratio)
• Quality of data
• Case definition (make sure the terminology refers to the same thing)
• Ascertainment (is the data complete)

Question 16

What are the four types of bias?

Answer 16

Selection, information, follow-up or systematic

Question 17

What is selection bias?

Answer 17

Sample is not truly representative of population

Question 18

What information bias?

Answer 18

Errors in measurement of data

Question 19

What is follow up bias?

Answer 19

Arises where one group happens to be more diligent in sending back data and this effects the conclusions of the test

Question 20

What is systematic bias?

Answer 20

A trend where measuring the results consistently falls on one side of the true measurement due to some implicit oversight

Question 21

What are confounding factors?

Answer 21

A cofounding variable influences both the dependent and the independent variable causing a spurious association

Question 22

What are the criteria for causality?

Answer 22

Strength of association 
Consistency 
Specificity 
Temporality 
Biological affect (dose-response relationship) 
Coherence 
Analogy 
Experimentation

Question 23

What is relative risk?

Answer 23

The measure of the strength of an association between a suspected risk factor and the disease under study

Question 24

How do you calculate relative risk?

Answer 24

Relative risk = Incidence of disease in exposed group / Incidence of disease in unexposed group