Epidemiology Key Concepts

Question 1

what forms the epidemiological triad?

Answer 1

• time
• place
• person

Question 2

what are the different sources of data for epidemiological enquiry?

Answer 2

• vital statistics
• disease registries
• notifiable diseases
• administrative systems
• health surveys
• special surveillance systems
• rapid community assessments

Question 3

what is point prevalence?

Answer 3

the proportion of a population that are cases at one point in time

Question 4

what is period prevalence?

Answer 4

the proportion of a population that are cases over a time period

Question 5

explain limitations of “crude” rates:

Answer 5

value limited when comparing two populations with different structures (i.e. confounding variable)

• two populations with same crude rates for a particular outcome (r.g. death) will have different overall rates if the distribution confounder (e.g. age) within populations are different

Question 6

what is standardisation?

Answer 6

a set of techniques, based on weighted averaging to remove as much as possible the effects of differences in age or other confounding variables in comparing two or more populations. the common method uses weighted averaging of rates specific for age, sex or some other potential confounding variables according to some specified distribution of these variables

The direct method of standardisation requires that the age-specific rates for all populations being studied are available and that a standard population is defined. The indirect method of standardisation requires the total number of cases

Question 7

what are age-adjusted mortality rates?

Answer 7

a weighted average of the age-specific mortality rates, where the weights are the proportions of persons in the corresponding age groups of a standard population

Question 8

what is the objective of an RCT study?

Answer 8

treatment effect

Question 9

what is the objective of a cohort study?

Answer 9

• cause
• prognosis
• incidence

Question 10

what is the objective of a case-control study?

Answer 10

cause

Question 11

what is the objective of a cross-sectional study?

Answer 11

prevalence

Question 12

which studies have a future time-frame?

Answer 12

• RCT

- cohort (prospective)

Question 13

which studies have a past time-frame?

Answer 13

• cohort (retrospective)
• case-control
• cross-sectional