Screening for Disease

Question 1

What are the 3 types of prevention?

Answer 1

• Primary prevention. Prevention of future occurrence in unaffected individuals by removing a cause.
• Secondary prevention. Prevention of clinical disease by screening, early detection and/or treatment.
• Tertiary prevention. In theory, prevention of disease by treating clinical cases.

Question 2

What are possible causes and interventions for disease?

Answer 2

• Environmental, economic, social, educational, and dietary factors.
• Remedying adverse causes and vaccination programmes.

Question 3

Why do we screen?

Answer 3

Obtain early diagnosis of a disease.

Question 4

What public health questions are asked when planning a screening test?

Answer 4

• Is the disease an important health problem?
• Can the disease be detected early?
• Is there a recognizable latent stage?
• Are facilities available for diagnosis and treatment?
• Is the cost of screening sufficiently low to make screening feasible?
• Does the cost of screening fit with other demands on financial resources?
• Is it clear whom should be screened?
• Is treatment beneficial?

Question 5

What is a gold standard test?

Answer 5

• Diagnostic test that is regarded as definitive in determining whether an individual has a disease
• Identifies all individuals with a disease process and does not falsely identify someone with a condition that does not have the condition

Question 6

How else can a true positive value be described?

Answer 6

• Sensitivity

- How well does the test detect the condition

Question 7

How else can a true negative be described?

Answer 7

• Specificity

- How good is the test at excluding those without the condition

Question 8

Define positive predicted value

Answer 8

If a person tests positive, the probability that he or she has the condition

Question 9

Define negative predicted value

Answer 9

If a person tests negative, the probability that he or she does not have the condition

Question 10

Define accuracy

Answer 10

The proportion of all tests that have given the correct result

Question 11

When is a high sensitivity or specificity appropriate?

Answer 11

• Sensitivity= Conditions that are treatable, and the treatment is not overly onerous
• Specificity= Conditions such as HIV

Question 12

What range of values is obtained for sensitivity & specificity?

Answer 12

0-1 or 0-100%