Epidemiology

Question 1

What is mortality rate?

Answer 1

Estimate of portion of population that dies during specified time period

Question 2

What do meaningful statistics in mortality rates need?

Answer 2

Denominator population

Time frame

Question 3

What is case fatality rate?

Answer 3

Proportion of cases of a specified condition that are fatal within a specified time

Question 4

What’s CFR?

Answer 4

Case fatality rate

Question 5

Weaknesses of CFR estimation:

Answer 5

Underestimation in early days of outbreak

Overestimation if denominator is limited (CFR only based on sub-group of cases)

Assumes all cases have been tested

Question 6

What does more testing allow with CFR rate?

Answer 6

Higher accuracy

Question 7

What is infection fatality rate?

Answer 7

Proportion of cases of a specified condition that die divided by total infected people

Question 8

What is IFR?

Answer 8

Infection fatality rates

Question 9

What does IFR accuracy depend on?

Answer 9

Detection and reporting of a symptomatic or mild symptom cases

Question 10

What is R0?

Answer 10

Reproduction number - number of cases that can be potentially infected by one case

Question 11

R0 < 1

Answer 11

Less likely spread of disease

Question 12

R0 > 1

Answer 12

More likely spread of disease

Question 13

Characteristics of R0:

Answer 13

Not biologically constant

Question 14

Give an example of calculating mortality rate:

Answer 14

50 people died of flu x100
——————————————-
Population of fife

Question 15

Give an example of person-time:

Answer 15

10 deaths per 10000 person years

Question 16

What can person years mean?

Answer 16

10000 people for 1 year

5000 people for 2 years

Question 17

Give example of n-year follow up:

Answer 17

5-year mortality of 10 per 10000 people

Question 18

When are death rates meaningless?

Answer 18

Without denominator population and time

Question 19

What is incidence?

Answer 19

Number of new cases

Question 20

Calculating incidence rate:

Answer 20

Number of new people with outcome over time period x100000
——————————————————————————————————
Total number of people (or person-time for people) in group at risk

Question 21

What’s prevalence?

Answer 21

Proportion of population that has disease

Question 22

What is point prevalence rate?

Answer 22

At a specified time

Question 23

Calculating point prevalence rate:

Answer 23

Number of people with outcome at a point in time x100
—————————————————————————————
Total number of people in group

Question 24

What’s period prevalence rate?

Answer 24

Over specified period

Question 25

Calculating period prevalence rate:

Answer 25

Number of people with outcome during time period x100 ——————————————————————————————- Average number of people in group

Question 26

Differences between incidence and prevalence:

Answer 26

Incidence can be rate or proportion whereas prevalence can only be a proportion

Question 27

Sporadic definition:

Answer 27

Occasional cases occurring irregularly

Question 28

Endemic definition:

Answer 28

Persistent background level of occurrence Low-moderate levels

Question 29

Outbreak definition:

Answer 29

Greater than expected cases of endemic levels

Question 30

Pandemic definition:

Answer 30

Occurring in more than one continent

Question 31

What are the different types of exposures?

Answer 31

Non-modifiable (e.g. age) Modifiable (e.g. weight) Interventions (e.g. drug therapy)

Question 32

How do you calculate risk?

Answer 32

Number of outcomes in group ———————————————— x100 Number if people in group

Question 33

How do you calculate relative risk?

Answer 33

Risk in exposed ————————— Risk in unexposed

Question 34

How do you calculate relative risk reduction?

Answer 34

(1 - Relative risk) x 100

Question 35

How do you calculate absolute risk reduction?

Answer 35

Risk in unexposed - risk in exposed

Question 36

How do you calculate number needed to treat?

Answer 36

1 ———————————— Absolute risk reduction

Question 37

What are confidence intervals?

Answer 37

Range of plausible values

Question 38

What does it mean if the confidence interval is wider?

Answer 38

Greater the uncertainty

Question 39

Cross-sectional study:

Answer 39

Sample population Estimate proportion + use data

Question 40

Case-control study:

Answer 40

Select cases with outcome and controls without outcome Explore exposures + compare Identify association

Question 41

Cohort study:

Answer 41

Select people with outcome + classify according to exposure Follow-up Compare risk of disease in exposed and unexposed

Question 42

Randomised controlled trial:

Answer 42

Random allocation Compare risk of outcome in intervention and control groups

Question 43

Objectives in cross-sectional:

Answer 43

Prevalence

Question 44

Objectives of case-control:

Answer 44

Cause

Question 45

Objective of cohort:

Answer 45

Cause Prognosis Incidence

Question 46

Objective of randomised controlled trial:

Answer 46

Treatment effect

Question 47

Time-frame of cross-sectional:

Answer 47

Past

Question 48

Time-frame of case-control:

Answer 48

Past

Question 49

Time-frame of cohort:

Answer 49

Prospective = future Retrospective = past

Question 50

Time-frame of randomised controlled trial:

Answer 50

Future

Question 51

What is confounding?

Answer 51

True relationship confused by third factor

Question 52

What may bias involve?

Answer 52

Systematic error (how data is used)

Question 53

What does bias lead to?

Answer 53

Wrong conclusion about effectiveness and causation