Lecture 7: Diagnostic and screening tests in respiratory disease

Question 1

Define a diagnostic test?

Answer 1

• confirmation of disease or otherwise
• results are mostly definitive
• applied to patients with clinical suspicion

Question 2

What is a screening test?

Answer 2

• identify patients who MAY have the disease
• results are preliminary and NOT definite
• applied to people with NO clinical suspicion

Question 3

What is sensitivity?

Answer 3

Probability of a true positive

Question 4

What is specificity?

Answer 4

Probability of a true negative

Question 5

Positive definitions for diseases (e.g. FEV1 for COPD or BP for hypertension) are expressed on a continuous scale. What happens to sensitivity and specificity if you increase or decrease threshold?

Answer 5

Increase threshold = ↑sensitivity, ↓specificity

Decrease threshold = ↓sensitivity, ↑specificity

Question 6

What is lead time bias?

Answer 6

Apparent improvement of survival times because of early screenings vs. someone who was diagnosed later without screening

Question 7

Name the 2 components of screening framework

Answer 7

CRITERA: used to determine wherever screening should be offered for certain conditions

KEY PRINCIPLES: for the implementation and management of screening programs