Ch 7b Sensitivity + Specificity Flashcards
What is FNV?
-False negative value
-The # of diseased persons testing negative
What is FPV?
-False positive value
-The # of non-diseased persons who tested positive
What is TD?
Total # of diseased persons
What is TN?
Total # of persons testing negative
What is TND?
Total # of non-diseased persons
What is TNV?
-True negative value
-The # of disease free persons testing negative
What is TOT?
Total # of persons in the study
What is TP?
Total # of persons testing positive
What is TPV?
-True positive value
-The # of diseased persons testing positive
Is the sensitivity for scrotal + OB exams high or low?
High - b/c u/s is the gold standard
If the test result is positive: list the correct definitions for the disease, non-diseased + total?
Disease: TPV (true positive value)
Non-diseased: FPV (false positive value)
Total: TP (total positive people)
If the test result is negative: list the correct definitions for the disease, non-diseased + total?
Disease: FNV (false negative value)
Non-diseased: TNV (true negative value)
Total: TN (total negative people)
List the total test results: list the correct definitions for the disease, non-diseased + total?
Disease: TD (total diseased people)
Non-diseased: TND (total non-diseased people)
Total: TOT (total people in study)
List the sensitivity formula?
SENS = TPV/TD
Define sensitivity?
-True positive rate
-The sensitivity of a test is the proportion of people with the disease who will have a positive result
A highly sensitive test is one that correctly identifies what?
Patients with a disease
A test that is 100% sensitive will identify what?
All patients who have the disease
List the specificity formula?
SPEC = TNV/TND
Define specificity?
-True negative rate
-The specificity of a test is the proportion of people without the disease who will have a negative result
The specificity of a test refers to how well a test identifies what?
Pt’s who do not have a disease
A test that has 100% specificity will identify what?
100% of pt’s who do not have the disease
Do high sensitivity tests have high or low specificity?
Low
(think they are inverse of each other)
High sensitivity + low specificity is good for catching actual cases of the disease. Do they have a high or low rate of false positives?
High false positive rate
(going to call pt’s back for more testing than they need to. A biopsy should be done)
Give an example of a test that generally has a high sensitivity (70-80%) + low specificity?
Mammograms
(sensitivity depends on tumor size, pt age, etc)