Screening

Question 1

What is screening?

Answer 1

The process of identifying healthy people who may have an increased chance of a disease or condition

Question 2

What are some benefits of screening?

Answer 2

• Save lives or improve quality of life through early identification of a condition
• Reduce the chance of developing a serious condition or its complication

Question 3

What is the Wilson and Jungner criteria in relation to the condition?

Answer 3

• Important public health problem
• Natural history understood
• Recognisable latent or early symptomatic phase

Question 4

What is the Wilson and Jungner criteria relating to the test?

Answer 4

• Simple, safe, precise and validated
• Acceptable
• Distribution of test results known and cut-off defined
• Agreed policy on further diagnostic investigations

Question 5

What is the Wilson and Jungner criteria relating to the treatment?

Answer 5

Effective and available

Question 6

What is the Wilson and Jungner criteria in relation to the screening programme?

Answer 6

• Evidence from RCTs that screening is effective/accurate
• Clinically, socially and ethically acceptable
• Cost effective
• Quality assured

Question 7

What is sensitivity?

Answer 7

How well the test picks up having the disease

Question 8

What is the equation for sensitivity?

Answer 8

Number of people with the disease

Question 9

What is specificty?

Answer 9

How well the test detects not having the disease

Question 10

What is the equation for specificity?

Answer 10

Number of people without the disease

Question 11

What is the difference between high sensitivity and high specificity?

Answer 11

Highly sensitive test:

• Picks up most of the disease
• Very few false negatives

Highly specific test:

• Correctly detects no disease
• Very few false positives

Question 12

What is the positive predictive value?

Answer 12

How reliable the test result which shows the disease is present is

Question 13

What is the equation for positive predictive value?

Answer 13

Number of people with a positive test result

Question 14

What is the negative predictive value?

Answer 14

How reliable the test result showing disease is not present is

Question 15

What is the equation for negative predictive value?

Answer 15

Number of people with a negative test result

Question 15

What is the equation for negative predictive value?

Answer 15

Number of people with a negative test result

Question 16

What are some potential harms of screening?

Answer 16

• False reassurance
• Over-investigation and treatment
• Anxiety
• Longer period of morbidity with unaltered prognosis
• Harm from screening test
• Opportunity costs
• Increased health inequalities