Sensitivity, Specificity, Positive Predictive Value, Negative Predictive Value

Question 1

define sensitivity (Sv), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV)

Answer 1

sensitivity: probability that the test is reactive (+) if the specimen is a true positive; high sensitivity = very few false negatives; good for ruling out diseases (trust the negative); false positives common!
-hella reactive, detecting things (could be a bomb in a suitcase at the airport or just shampoo but will beep either way)
-sensitivity rules out (SNOUT)
-proportion of disease animals that test positive, ability of test to detect those with disease

Question 2

define specificity

Answer 2

specificity: probability that the test will not be reactive (-) if a specimen is a true negative; highly specific = few false positives; good for ruling IN diseases (trust the positive)
-specificity rules in (SPIN)
-proportion of non-diseased animal that test negative, ability of test to detect those without disease

Question 2

define positive predictive value

Answer 2

how well does the beep predict shampoo or not shampoo; what does the beep/test mean and how do we apply to patient?

positive predictive value: the proportion of cases giving positive test results who are already patients/positive;

the ratio of patients truly diagnosed as positive to all those who had positive test results (including healthy subjects who were incorrectly diagnosed as a patient)

-this can predict how likely it is for someone to truly be a patient in case of a positive test result

-depends on the population being tested; relies on prevalence of disease in a population

ratio: patients diagnosed positive:patients with positive test

Question 3

define negative predictive value

Answer 3

negative predictive value: the proportion of the cases giving negative test results who are actually healthy;

the ratio of the subjects truly diagnosed as negative to all those who had negative test results (including patients who were incorrectly diagnosed as healthy)

-this can predict how likely it is for someone to be truly healthy in the case of a negative test result

Question 4

apply the concepts of sensitivity and specificity to evaluate the appropriateness of diagnostic tests in various clinical scenarios

Question 5

interpret Sv, Sp, PPV, and NPV in the context of diagnostic test performance

Answer 5

cannot be sensitive AND specific!! need to be on or the other

Question 6

select diagnostic tests based on the required balance between sensitivity and specificity for various conditions