EBM Flashcards
Define: Sensitivity
The probability that a test will be a true
positive in a person with the disease. Sensitivity relates to the test’s ability to identify a condition correctly.
Define: Specificity
The probability that a test will be a true negative in a person who does not have the disease. Specificity relates to the test’s ability to exclude a condition correctly.
Define: Positive Predictive Value
The probability that a person with a positive test has the disease
Define: Negative Predictive Value
The probability that a person with a negative test does not have the disease
Draw a 2x2 Table for calculate EBM statistics
Test result on the left (First row: positive test, Second Row: Negative test)
Disease State on the top (First column: has the disease, Second Column: does not have the disease)
How do you calculate the Sensitivity
Number with disease with a positive test / number with the disease.
A / A+C
How do you calculate the Specificity
Number without the disease with a negative test result / Number without the disease.
D/D+B
How do you calculate the Positive Predictive Value
Number with disease and a positive test result / number of people with a positive test result.
A/A+B
How do you calculate the Negative Predictive Value
Number with disease and a negative test result / number of people with a negative test result.
D/C+D
What is the pre-test probability the equivalent of?
Prevalence
SnNout
Negative results from highly sensitive tests can rule a diagnosis out (sensitive, negative, out = SnNOut), and
SpPin
Positive results from highly specific tests can rule a diagnosis in (specific, positive, in = SpPIn)
Which of the four EBM statistical values are altered by changes in the prevalence of the disease?
PPV and NPV.
