Diagnostic tests

Question 1

What are some reasons for doing diagnostic tests?

Answer 1

To increase the amount of evidence to help you draw a clinical conclusion
To increase the certainty of a diagnosis
To obtain a diagnosis
To confirm a patient has a disease
To narrow down the differential list 
To confirm a disease is present
To quantify the severity of infection 
To localise the infection

Question 2

What are the steps in a diagnostic process?

Answer 2

History
Clinical exam
Differential diagnosis list

Question 3

What is a diagnostic test?

Answer 3

A procedure that generates information used in generating a diagnosis

Question 4

Define sensitivity and specificity

Answer 4

Sensitivity - the ability to detect individuals who have disease
Specificity - the ability to detect individuals who do not have disease

Question 5

What is the positive predictive value and the negative predictive value?

Answer 5

PPV = the likelihood that an individual with a positive test result actually has the disease
NPV = the likelihood that an individual with a negative test result does not have the disease

Question 6

What is the accuracy of a test the sum of?

Answer 6

True positives and true negatives over the overall total

Question 7

What is sensitivity the sum of?

Answer 7

True positives and false negatives

Question 8

What is specificity the sum of?

Answer 8

False positives and true negatives

Question 9

What is true prevalence the sum of?

Answer 9

Total disease positive = true positives + false negatives

Question 10

What is the apparent prevalence the sum of?

Answer 10

Test positives = true positives + false positives

Question 11

What is the PPV the sum of?

Answer 11

True positives / (true positives + false positives)

Question 12

What is the NPV the sum of?

Answer 12

True negatives / (true negatives + false negatives)

Question 13

What is a type 1 error?

Answer 13

Rejecting a true null hypothesis e.g. saying there is evidence of an effect when there is no effect

Question 14

What is a type 2 error?

Answer 14

Accepting a false null hypothesis e.g. saying there is no effect when there is one

Question 15

What is a paired t-test?

Answer 15

A statistical test that is used to compare the means of two groups

Question 16

What is a non-paired t-test?

Answer 16

Comparing sets of continuous data from two populations