# Lecture 2 Flashcards

1
Q

prevalence formula

A
```# people who have disease at given point in time
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
# of people in population of interest```
2
Q

cumulative incidence formula

A
```# new cases of disease in a given time period
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
# people who can develop that disease```
3
Q

prevalence in relation to incidence and duration

A

prevalence = indidence x average duration

4
Q

prevalence

A
• the probability of having a disease at at given point in time
• the pre-test probability
• how common a disease is
• gives you baseline probability
5
Q

incidence

A
• the proportion of new cases of disease in the population at risk of getting the disease over a given period of time
• also known as risk
• tells you about what could happen in the future
6
Q

incidence versus prevalence

A
• incidence based on new cases
• prevalence based on new and old
• incidence based on cases that develop over a specified period of time
• prevalence is based on cases that exist at a single point in time
7
Q

incidence density

A
• the number of new cases of disease that develop over a given time period divided by person-time at risk of disease
8
Q

if incidence increases and average duration remains the same

A
• prevalence increases
9
Q

if average duration of a disease increases and incidence stays the same

A
• prevalence increases
10
Q

attack rate

A
• the proportion of people who develop the disease, among those at risk, during a specified time period
11
Q

attack rate formula

A

new cases of disease in a given time period
___________________________________
persons at risk

12
Q

case fatality rate

A
• the proportion of people affected with a disease who die from it, in a given time period
13
Q

case fatality rate formula

A

deaths from a disease in a given time period
____________________________________
number of persons who have that disease

14
Q

mortality rate

A
• the proportion of people who die, among those at risk of death, in a given time period
15
Q

mortality rate formula

A

deaths in a given time period
__________________________
population at risk of dying

16
Q

how to get estimates of pre-test probability?

A
• knowledge of prevalence in your clinical site
• medical literature
• clinical predictions
• clinical experience
17
Q

test threshold

A
• separates “don’t test, don’t treat” zone from “test” zone
18
Q

treat threshold

A
• separates “test” zone from “don’t test, treat” zone
19
Q

determines where the thresholds are set

A
• accuracy of test
• risk of test
• seriousness of illness and benefit of treatment
• risk of treatment
20
Q

accuracy of test

A
• test threshold will be lower for more accurate tests
21
Q

risk of test

A
• test threshold will be higher for more risker; invasive tests
22
Q

seriousness of illness and benefit of treatment

A
• test and treatment thresholds will be lower for serious illnesses with beneficial treatment
23
Q

risk of treatment

A
• treatment threshold will be higher for riskier treatment
24
Q

if pre-test probability is below test threshold

A
• not wise to test for the condition at all because a positive test is more likely to be a false positive than a true positive
25
Q

rule in

A
• moved above treat threshold
26
Q

rule out

A
• moved below test threshold
27
Q

if pre-test probability is above the treat threshold

A
• don’t test, just treat
28
Q

pattern recognition

A
• one of the most efficient diagnostic strategies used by seasoned clinicians
29
Q

point prevalence

A
• measured at a single point in time for each person
30
Q

period prevalence

A
• describes cases that were present at any tine during a specified period of time
31
Q

another name for prevalence studies

A
• cross-sectional studies

- people are studied at a “cross-section” of time

32
Q

cohort

A
• population under examination in an incidence study
• group of people having something in common when they are first assembled and are then followed over time for the development of outcome events
33
Q

another name for incidence studies

A
• cohort studies
34
Q

cumulative incidence

A
• describe the rate of new events in a group of people of fixed size, all members of which are observed over
a period of time.
• new cases are accumulated over time
35
Q

incidence density

A
• to measure the number of new cases emerging in an ever-changing population, one in which individuals are under study and susceptible for varying lengths of time.
• common for clinical trial companies
36
Q

denominator of incidence density measure

A
• person-time
37
Q

dynamic populations

A
• those in which some individuals in the population are entering and others leaving as time passes