Unit 3

Question 1

Screening tests

Answer 1

used as a population aooraoch on apparently helaht individuals to detect sub clinical disease

Question 2

Diagnostic test

Answer 2

used on sick individuals with critical disease to confirm and classify patricular disease

Question 3

Sensitivity (Sn)

Answer 3

the ability of a test to identify correctly those who have the disease or outcome of interest

proportion of outcome postiive that atuacylly have

Sn= a/ (a+c)

as Sn increases the number of false negatives decrease

Question 4

Specificty

Answer 4

the ability of a test to idenifty correctly those that do not hae the disease or outcome of interest

proportion of outcome negative that are acurally dont have it

Sp = d (b+d)

As Sp increases the number of false positive decreases

Question 5

True prevalence

Answer 5

the acutaly proportion of disease within a poulation

TP=a+c/n

Question 6

Apparent prevalence

Answer 6

the observed proporiton of disease within a population

AP= a+b/n

Question 7

Positive predicitve value

Answer 7

the predictive value of a positive test result, the proportion of test positivest that acually have disease

PPV= a/(a+b)

Question 8

Negative predictive value

Answer 8

the predictive value of a negative test result, the proportion of test positives that actually do not have the disease or health outcome

NPV=d/(c+d)

Question 9

Series testing def, pros and cons

Answer 9

tests are used one after another in sequence, only those that test positive are then tested with the subsequent test

pros-less expensive but invasive. aims to avoid false positive, however will miss the disease positive individual that tested negative eon the first test

**loss in net sensitivity and gain in specificty

Question 10

Parallel testing def, pros and cons

Answer 10

multiple tests are used simultaneously to determine final decisions

more expensive, can be more invasive and taxing, good at preventing false negatives, individuals need to get a negative result on both tests in order to be deemed disease free

**gain in net sensitivity and loss in net specificty

Question 11

Chance agreement

Answer 11

situations where tow indivudlas make the same assessment due to ranom change alone rahter then true agreement

Question 12

Kappat statisitc

Answer 12

a measure of agreement beyond what would chance alone

observed agreement - expceted/ (1-expected)

0.8 excellemt agreement