Measures of disease frequency Flashcards
What is prevalence?
no. of existing cases in a defined population at a specific point in time divided by no. of people in the population at that time
Describe the 2 diff ways prevalence can be monitored
actively - seek out ppl w disease
or
passively - taken from data at at GP practices or anonymous info that is given
What is incidence?
no. of new cases in a population during a specific time period
What are the 3 types of incidence?
RISK
odds
incidence rate
What is risk>
refers to total no. of new cases in a defined population at risk over a time period
or
likelihood that individuals will develop an outcome during time period
What is odds ratio
odds of disease if exposed: odds of disease if not exposed
How do you work out odds ratio?
(no. of new cases in specified Time period) / (no. who didn’t become a case during time period)
What is secondary attack rate?
no. of new cases among contacts (people exposed to person w disease) in a specified time/ total no. of contacts of a primary case in that time
What is relative risk?
the ratio of the risk of disease in persons exposed compared to the risk of disease in persons unexposed
What is absolute risk?
( number of events (good or bad) in treated or control group ) / ( number of people in that group)
What is absolute risk reduction (ARR)?
AR of events in the control group (ARC) - AR of events in the treatment group (ART)
What is NNT
1/ARR
