Epi Chp 3

Question 0

Which method (passive or active surveillance) is more accurate?

Answer 0

Active surveillance

Question 1

Describe the difference between passive surveillance and active surveillance

Answer 1

Passive surveillance- denotes surveillance with already available data (healthcare providers, health departments-using data from places that have already collected the data)

Active surveillance-a system in which staff are recruited to carry out a surveillance program

Question 2

What are some of the drawbacks to active surveillance?

Answer 2

More expensive

More difficult to develop initially

In developing countries-areas of need difficult to reach, difficult to maintain communication

Question 3

Occurrence of disease can be measured using rates or proportions. What do rates tell us versus proportions?

Answer 3

Rates-tell us how fast the disease is occurring in a population

Proportions - tell us what fraction of the population is affected

Question 4

define INCIDENCE rate

Answer 4

Incidence rate is defined as the number of new cases of a disease that occur during a specified time in a population at risk for developing the disease.
OR
incidence rate per 1,000=

# new cases of disease occurring in a population @ a specific time
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
# of people at risk of the same disease during the same time

Question 5

What is the CRITICAL element in defining incidence rate?

Answer 5

NEW cases of disease

Question 6

Is the incidence rate a measure of disease?

Answer 6

Yes
because the incidence rate is a measure of events (i.e. transition from a non diseased to diseased state), the incidence rate is a measure of risk.

Question 7

What does the denominator of an incidence rate represent?

Answer 7

the number of people who are at risk for developing the disease.

Question 8

What must occur when assessing incidence rate in order for incidence rate to be meaningful?

Answer 8

For an incidence rate to be meaningful, any individual who is included in the DENOMINATOR MUST have the potential to become part of the group that is counted in the numerator

Question 9

Incidence measures can use 2 types of denominators (time), what are they?

Answer 9

people at risk who are observed throughout a defined time period
OR
when all people are not observed for the full time period

Question 10

If trying to assess incidence and the observed populations are observed for different time periods what formula should be used?

Answer 10

Incidence rate per 1000 equals

total # people observed (sum of both)

Question 11

Define prevalence

Answer 11

The number of affected people present in the population at a specific time
————————————— number of people in the population at that time

(what proportion of the population is affected by the disease at that time)

Question 12

What is the difference between incidence and prevalence?

Answer 12

Prevalence-can be viewed as a snapshot or a slice through the population at a point in time-we determine who has the disease and who does not

Prevalence will not give a measure of risk (because typically we do not take into account the duration of the disease)

Question 13

What are the two types of prevalence

Answer 13

Point prevalence-prevalence of the disease at a certain point in time

Period Prevalence - how many people have had the disease at any point during a certain time period.

Question 14

For each question below answer what type of measure the question asks?

Have you had asthma during the last year?

Have you ever had asthma?

Do you currently have asthma?

Answer 14

Period Prevalence-have you had as much during the last year

Cumulative incidence-have you ever had as my

Point prevalence-do you currently have asthma

Question 15

When we see the word prevalence used without any modifier it generally refers to what kind of prevalence?

Answer 15

Point prevalence

Question 16

We know that incidence counts only what

Answer 16

New cases

Question 17

When starting a intervention for diabetes care what should one expect about the prevalence rate, and incidence rate?

Answer 17

Incidents should eventually decrease

Prevalence will increase however-because there are fewer people dying from diabetes

Question 18

So if prevalence is not a measure of risk why bother estimating prevalence?

Answer 18

Prevalence is an important and useful measure of the burden of disease in a community

Prevalence is also used for planning health services

Question 19

What are some of the difficulties that arise with incidence and prevalence measurements?

Answer 19

Defining who has the disease

Prevalence estimates can be significantly affected by the set of criteria that is used

Issues relating to the numerator are ascertaining which person should be included in the numerator (Passive versus active surveillance)

Problems with denominators:
Selective under counting of certain groups
Different ways to classify people in ethnic groups

Question 20

List problems with hospital data

Answer 20

Severity of disease

Incomplete records

Illegible or missing records

Diagnostic quality of records may differ

Question 21

Explain the relationship between incidence and prevalence

Formula?

Answer 21

Incidence is a measure of risk and prevalence is not

Prevalence does not take into account the duration of disease

(Look up formula and put in here)

Question 22

What would be the effect on age-specific incidents rates of uterine cancer if women with hysterectomies were excluded from the denominator of the calculations, assuming that there are some women in each group who have had hysterectomies?

Answer 22

The rates would tend to increase

Question 23

What is the biggest advantage of active surveillance?

Answer 23

Greater accuracy due to reduced reporting burden for healthcare providers