PH: Principles of Screening

Question 1

Define ‘detection rate’

Answer 1

proportion of affected individuals with positive results.

Question 2

Define ‘false-positive rate’

Answer 2

1-specificity = proportion of unaffected individuals with positive results

Question 3

How do you calculate OAPR? (odds of being affected given a positive result)

Answer 3

true positives : false positives

likelihood ratio x prevalence as odds

Question 4

How is the odds of being affected given a positive result (OAPR) in screening affected?

Answer 4

It’s affected be the prevalence of the disorder in a screened population, the higher the prevalence, the greater the OAPR

Question 5

How do you calculate the likelihood ratio from screening results?

Answer 5

Detection rate/false-positive rate

Question 6

How can you calculate the OAPR from likelihood and prevalence?

Answer 6

(likelihood ratio x prevalence as odds)

Question 7

What’s the difference between probability and odds?

Answer 7

probability presents the number of affected against the total population (1/5) whereas odds is the number of affected to the number of unaffected (therefore would be 1:6)