Diagnostic tests

Question 1

What is test accuracy?

Answer 1

A comparison between the disease state estimated by the test and the best estimate of the true disease state

Question 2

What is the index test?

Answer 2

This is the diagnostic test being evaluated

Question 3

What is the reference standard?

Answer 3

This is the best way of detecting the condition and the index test is being compared against it

Question 4

What is spectrum bias?

Answer 4

This is an error due to difficult to diagnose patients being purposefully excluded - this will make the index test seem more accurate than it actually is

Question 5

What is verification bias?

Answer 5

There is a tendency of patients with negative index tests not to get the reference standard - this effects the index test results

Question 6

What is review bias?

Answer 6

If interpretation of the index test is not seperate to the reference standard

Question 7

What is sensitivity? how is it measured?

Answer 7

Sensitivity tells us how accurate a test is in individuals with disease and the magnitude of false negatives
It is calculated by true positives over true positives + false negative

Question 8

What is specificity? how is it measured?

Answer 8

Specificity tells us how accurate a test is in individuals without the condition and the magnitude of false positives.
It is calculated by true negatives over all those without the disease (TN and FP)

Question 9

What does a 95% confidence interval mean?

Answer 9

95% of the time the result will lie between these values

Question 10

How do you calculate the number needed to treat?

Answer 10

1 over the risk difference