Epidemiology in Practice

Question 1

Define ‘population excess fraction’

Answer 1

The proportion of the cases observed in the study population attributable to the exposure of interest

Question 2

When is the perinatal period?

Answer 2

The period immediately before and after birth - typically a few weeks in either direction.

Question 3

Define incidence

Answer 3

The number of new cases in a given time interval

Question 4

Define prevalence

Answer 4

The frequency of a disease in a population at a point in time.

Question 5

What are proximal factors?

Answer 5

Factors measured in clinic, such as blood pressure

Question 6

What are distal factors?

Answer 6

Factors measured upstream, such as socioeconomics, poverty and inequality.

Question 7

Define epidemiological transition

Answer 7

Decline in total mortality
Significant reduction in infectious and deficiency diseases
Increase in chronic, non-communicable diseases.

Question 8

How many cancers have an inherited component?

Answer 8

1% –> 99% are sporadic.

Question 9

What is specificity?

Answer 9

Ability to correctly identify those without the disease (true negative).

Question 10

What is sensitivity?

Answer 10

Ability to correctly identify those with the disease (true positive).

Question 11

Give the hierarchy of study designs.

Answer 11

1a: systematic review of RCTs, meta-analysis
1b: single RCT with narrow confidence interval
1c: All or none case series (all patients died before a new therapy introduced - all now survive)
2a: systematic review of cohort studies
2b: individual cohort study or RCT with <80% follow-up
2c: outcomes research
3a: systematic review of case-control studies
3b: case control study
4: case report/series
5: expert opinion

Question 12

What is the standardised mortality rate?

Answer 12

The rate ratio adjusted for age. An SMR for bladder cancer of 1.70 in the exposed group would mean that there is 70% more cases of death due to bladder cancer in the cohort than in the reference population.

Question 13

What is the relationship between probability and odds?

Answer 13

Odds = probability / (1-probability)

Question 14

Define attributable risk.

Answer 14

Incidence in exposed - incidence in unexposed.

Question 15

What is primary prevention?

Answer 15

Prevention of disease of injury before it occurs.

Question 16

What is secondary prevention?

Answer 16

Reducing the impact of a disease or injury which has already occurred (detecting as soon as possible).

Question 17

What is tertiary prevention?

Answer 17

The aim of softening the impact of an ongoing disease or illness which has lasting effects.

Question 18

What is a cross sectional study?

Answer 18

An observational study which analyses data from a population at a particular point in time.

Question 19

What is the healthy worker effect / healthy user bias?

Answer 19

Sampling bias: those who voluntarily enrol in a clinical trial and follow the advice are not representative of the whole population and can be expected to be, on average, healthier.

Question 20

What is the difference between a cohort study and a case-control study?

Answer 20

Cohort study has no control group and is PROSPECTIVE.

Case-control study compares cases to controls and is RETROSPECTIVE.

Question 21

What is primordial prevention?

Answer 21

Prevention of factors promoting the emergence of lifestyles, behaviours, exposure patterns which contribute to increased risk of disease.

Question 22

What does NTD stand for and give some examples.

Answer 22

Neglected tropical diseases.
Intestinal worms
Schistosomiasis
Leprosy

Question 23

What are the strategies used to treat NTDs?

Answer 23

Diagnosis and treatment: leprosy and sleeping sickness

4 drugs used to provide annual mass treatment for the rest.

Question 24

What is the difference between a meta analysis and a systematic review?

Answer 24

A meta-analysis is a statistical procedure for combining numerical data from multiple separate studies.
A systematic review is a detailed, systematic and transparent means of gathering, appraising and synthesising evidence to answer a well-defined question.

Question 25

What does a symmetrical funnel plot suggest?

Answer 25

There is no publication bias.

Question 26

What four factors are used to evaluate association?

Answer 26

Chance, confounding, causality, bias.

TEMPORAL RELATIONSHIP used to assess causality.

Question 27

How can confounding variables be controlled for at the analysis stage of discussion?

Answer 27

By REGRESSION.

Question 28

What is the difference between sensitivity and PPV?

Answer 28

Sensitivity = ability (of the screening test)
PPV = likelihood

Question 29

What could cause incidence and prevalence to increase respectively?

Answer 29

Incidence could increase by better diagnosis and treatment

Prevalence could increase by sufferers living longer.

Question 30

What are the four drugs used for the mass treatment of NTDs?

Answer 30

Mectizan, Albendazole, Zithromax, Prazuquantel

Question 31

What is lead time bias?

Answer 31

The time between detection and normal presentation. If you pick something up earlier from screening they might not actually live longer than if they’d waited until it was noticeable but it seems as though the time from detection to death is longer.

Question 32

Match the drugs to their NTDs

Answer 32

Praziquantel: schistomiasis
Albendazol - helminths and LF
Mectizan; onchoceriasis and LF
Zithromax - blinding trachoma

Question 33

Match the NTDs to their animal vectors.

Answer 33

Schistomiasis - snails
Lymphatic filiaris - mosquito
Onchoceriasis - blackfly