epidemiologic data mesurment

Question 1

Measures existing cases of disease and is expressed as a proportion

Answer 1

Prevalence

Question 2

Measures be cases of disease and is expressed in person-time units

Answer 2

Incidence

Question 3

of a disease, injury, or death can be measured in different ways, and it can be related to different denominators

Answer 3

Frequency
- depending on the purpose of the research and the availability of data

Question 4

is the frequency of occurrences of disease, injury, or death that is, the number of transitions from well to ill, from uninjured to injured, or from alive to dead—in the study population during the time period of the study

Answer 4

Incidence (Incident Cases)

• better to use the term incident cases
• cases from before are also recorded not only those within the time span
• measures new cases of disease and is expressed in person-time units

Question 5

is the number of persons in a defined population who have a specified disease or condition at a given point in time, usually the time when a survey is conducted

Answer 5

Prevalence (prevalent cases)
- sometimes called point prevalence
- measures existing cases of disease and is expressed as a proportion

Question 6

Difference between point prevalence and period prevalence

Answer 6

Index card

Question 7

Line graph -
Bar graph -

Answer 7

Line graph - incidence
Bar graph - prevalence

Question 8

It is defined as the proportion of persons who are unaffected at the beginning of a study period, but who experience a risk event during the study period

Answer 8

Risk

Question 9

True or false:
Rates are often used to estimate risk

Answer 9

True

Question 10

measuring only those that are recorded in that time span

Answer 10

period prevalence
- involves a time period

Question 11

the proportion of individuals in a population (initially free of disease) who develop the disease within a specified time interval

Answer 11

risk

Question 12

It is the number of events that occur in a defined time period, divided by the average number of people at risk for the event during the period under study.

Answer 12

rate
- measured in person time units

Question 13

this also measure the frequency of new cases of disease in a population

Answer 13

rate
- takes into account the sum of the time that each person remained under observation and at risk of developing the outcome under investigation

Question 14

What does specificity measure in diagnostic testing?

Answer 14

The percentage of true negatives (e.g., 90% specificity means 90% of people who do not have the target disease will test negative).

Question 15

What does a specific test help with when the test result is positive?

Answer 15

It helps rule out a disease.
[it confirms the disease]

Question 16

The probability that following a positive test result, the individual truly has the specific disease.

Answer 16

Positive Predictive Value (PPV)

Question 17

How does prevalence affect PPV?

How does prevalence affect NPV?

Answer 17

As prevalence decreases, PPV decreases because there are more false positives for every true positive.

As prevalence decreases, NPV increases because there are more true negatives for every false negative.

Question 18

The probability that following a negative test result, the individual truly does not have the specific disease.

Answer 18

Negative Predictive Value (NPV)

Question 19

What does NPV help clinicians determine?

Answer 19

How likely it is that a patient truly does not have a specific disease following a negative test result.

Question 20

What is a risk event in epidemiology?

Answer 20

A risk event may be death, disease, or injury, and the people at risk for the event at the beginning of the study period constitute a cohort.

Question 21

In a cohort study, how does the denominator for calculating risk change over time?

Answer 21

The denominator does not change unless people are lost to follow-up.

Question 22

Why is the denominator for a 5-year risk of death or disease the same as for a 1-year risk in a cohort study?

Answer 22

cos the denominator is the number of persons counted at the beginning of the study.

[In a cohort study, the denominator is the group of people being studied from the beginning. This doesn’t change whether you’re looking at risks over 1 year or 5 years.]

Question 23

What is the general formula for calculating a rate?

Answer 23

Rate= Denominator/ Numerator
×ConstantMultiplier.

Question 24

Why are rates multiplied by a constant multiplier?

Answer 24

To make the numerator larger than 1, making the rate easier to interpret (e.g., “one death per thousand people per year”).

Question 25

How are rates related to risk in epidemiology?

Answer 25

rates are often used to estimate risk.

Question 26

When is a rate a poor approximation of risk?

Answer 26

if the event in the numerator occurs only once per individual during the study interval.
If the proportion of the population affected by the event is small (e.g., <5%).
If the time interval is relatively short.