Screening

Question 1

Secondary prevention

Answer 1

the reduction in the expression and severity of clinical disease, delays onset and duration of clinical disease, goal is to improve survival

Question 2

Tertiary prevention

Answer 2

goal is to slow or block the progression of a disease, implemented after a clinical diagnosis has been made

Question 3

reliability

Answer 3

the ability to give the same result on repeated testing, influenced by stability, technical characteristics of the test method, and observer agreement among those conducting the test

Question 4

sensitivity

Answer 4

the probability that a test correctly classifies positive individuals who have preclinical disease

Question 5

sensitivity formula

Answer 5

= # of individuals with disease who test positive / # of individuals with disease x 100

a / (a + c)
“true positives (box a)”

Question 6

specificity

Answer 6

probability that a test correctly classifies individuals without preclinical disease as negative

Question 7

specificity formula

Answer 7

= # of individuals without disease who test negative / # of individuals without disease

d / (b + d)
“true negatives (box d)”

Question 8

False Positive

Answer 8

Box B

Tested positive but do NOT have disease

Question 9

False negative

Answer 9

Box C

tested negative but DO have disease

Question 10

Positive predictive value (PPV)

Answer 10

proportion of individuals with a positive test who have preclinical disease as a percentage

Question 11

PPV formula

Answer 11

of individuals who test positive and have disease / # of individuals who test positive x 100

a / (a + b)

Question 12

Negative predictive value (NPV)

Answer 12

proportion of individuals without disease who test negative as a percentage

Question 13

NPV formula

Answer 13

individuals who test negative and DO NOT have disease / # of individuals who test negative x 100

d / (c + d)

Question 14

Diagnostic Accuracy (Precision)

Answer 14

Proportion of time that a patient is correctly identified as either having a disease or not having a disease with a (+) or (-) test

Question 15

DA (DP) formula

Answer 15

= (TP + TN) / all patients x 100

Question 16

Likelihood Ratio Positive (LR+)

Answer 16

probability of a positive test in the presence of disease / probability of a positive test in the absence of disease

should be > 10 for most beneficial

Question 17

LR+ formula

Answer 17

= sensitivity / (1-specificity)
or
[a / (a + c)] / [b / (b + d)]

Question 18

Likelihood Ratio Negative (LR-)

Answer 18

Probability of a negative test in the presence of disease / probability of a negative test in the absence of disease

should be < 0.1 for most beneficial

Question 19

LR- formula

Answer 19

= (1-sensitivity) / specificity

Question 20

Validity

Answer 20

ability to accurately discern between those that do have the disease and those that do not have the disease

Question 21

internal validity

Answer 21

extent to which results accurately reflect the true situation of the study population

Question 22

external validity

Answer 22

extent to which results are applicable to other populations not included in the original study (how similar study peeps to your patients)

aka generalizability

Question 23

Primary prevention

Answer 23

maintenance of health through individual or community efforts so the disease process never starts (reduces incidence)