Descriptive epidemiology

Question 1

Definition of evidence-based medicine

Answer 1

The application of clinical epidemiology to the care of the patient.

• Formulating specific ‘answerable’ clinical questions
• Finding the best avalable research evidence bearing on that question
• Judging the evidence for its validity
• Integrating the critical appraisal with the clinicians expertise an dthe patients situation and values.

Question 2

Define descriptive epidemiology

Answer 2

Descriptive epidemiology identifies how disease is distributed and determines what hypothesis might explain that distribution.

Question 3

Prevalence definition

Answer 3

Prevalence is the fraction (proportion of percent) of a group of people possessing a clinical conditio of outcome at a given point in time.

Prevalence refers to existing cases in the population divided by the number of people in the population.

Question 4

Incedence definition

Answer 4

Refers to the fraction or proportion of a group of people initially free from the outcome of interest that develop the conidition over a given period of time.

Incidence refers to new cases in the population divided by the number of people in the population at risk of developing the disease or outcome of interest.

Question 5

Relationship between prevalence, incidence and duration of disease

Answer 5

Anything that increases the duration of disease increases the chances that the patient will be identified in a prevalence study.

Question 6

Incidence density

Answer 6

Also called ‘incidence rate’

Incidence density = no. of disease onsets / person years

Question 7

Cumulative incidence

Answer 7

Also called ‘incidence proportion’

**Cumulative incidence = **no. of disease onsets / no. initially at risk

Question 8

Important characteristics for the denemonitor when calculating rate

Answer 8

The characteristics of the denominator are espcially important:

1. All members of the population should comprise a population at risk
2. The population hsould be relevant to the question
3. The population should be described in sufficient detail so a judgment can be made about the generalisability of the result to the types of patients you are interested in.

Question 9

Types of sampling

Answer 9

1. Simple random sampling
   
   • Every individual in the population has an equal probability of being selected
2. Probability sampling
   
   • _​​_Every person has a known (not necessarily equal) probability of being selected. Useful when attempting to get equal representation in the sample of minority groups (i.e. elderly, ethnic groups etc). Investigators can increase the sampling fraction and over sample low-frequency groups
3. Non-random sampling
   
   • ​​Convenience samples (i.e. patients who are visiting a medical facility, are articulate cooperative)
   • Grab samples (grab patients wherever they can find them)
   • Many represent biased sample of their patient population

Question 10

Epidemic

Answer 10

An epidemic is a concentration of new cases in time.

Question 11

Pandemic

Answer 11

Used when a disease is widespread such as a global epidemic.

Question 12

Endemic

Answer 12

When a disease is limited to certain places.

Question 13

Distribution of disease by person

Answer 13

When disease affects certain kinds of persons at the same times and in the same places as other people who are not affected, this gives clues to causes and guideance on how health care efforts should be deployed.

Question 14

What is the importance of prevalence studies and what are they not good for?

Answer 14

Strengths

• The prevalence of diseease strongly affects the interpretation of diagnostic test results.
• It is an important guide to planning health services

Weaknesses

• Weak evidence for cause and effect
• Prevalence may be a result of incidence of disease or duration of disease. Not able to determine how much incidence and duration of disease contribute to prevalence.