Session 8: Screening

Question 1

What are the 5 areas of criteria for implementing a screening program?

Answer 1

1. Condition
2. Test
3. Intervention
4. Screening program
5. Implementation

Question 2

What is the criteria relating to the condition about?

Answer 2

It must be an important health problem with epidemiology, incidence, prevalence and natural history understood.

Question 3

What is the criteria relating to the test about?

Answer 3

It must be a simple, safe, precise and validated screening test

Question 4

What is the criteria relating to the intervention about?

Answer 4

Effective intervention for patients identified through screening, with evidence that intervention at a pre-symptomatic phase leads to better outcomes compared to usual care

Question 5

What are 3 points about the criteria relating to the screening program?

Answer 5

proven effectiveness in reducing mortality or morbidity
clinically, socially and ethically acceptable
benefit > harms
Opportunity cost economically balanced

Question 6

What is the criteria relating to the implementation about?

Answer 6

Clinical management and patient outcomes should be optimized
All other options considered
Quality assurance through management and monitoring programs
Adequate resources
Evidence-based information available, informed choice

Question 7

What are the advantages of screening?

Answer 7

Better outcome compared to finding something in the usual way

Question 8

What are the disadvantages of screening?

Answer 8

Overdiagnosis

Cost

Question 9

What are 3 evaluation difficulties concerning screenings?

Answer 9

1. Lead time bias
2. Length time bias
3. Selection bias

Question 10

What is lead time bias?

Answer 10

Early diagnosis falsely appears to prolong survival

Question 11

What is length time bias?

Answer 11

Lead to false conclusion that screening is beneficial in lengthening the lives of those found positive but instead they could have still lived to the same time

Question 12

What is selection bias?

Answer 12

Those who have regular screening likely to also do other things that minimizes risk factors

Question 13

What are false positives?

Answer 13

Refer well people for further investigations

Question 14

What are false negatives?

Answer 14

Fail to refer people who do actually have an early form of disease

Question 15

What are the 4 features of test validity?

Answer 15

Sensitivity
Specificity
Positive predictive value
Negative predictive value

Question 16

What is sensitivity?

Answer 16

How good the test is at picking up the disease

Question 17

How do you calculate sensitivity?

Answer 17

People with the disease who test positive over total people with disease

Question 18

What is specificity?

Answer 18

How good the test is at ruling out people who do not have the disease

Question 19

How to calculate test specificity?

Answer 19

People without disease and got tested negative over total people without disease

Question 20

What is positive predictive value?

Answer 20

Probability that someone who has tested positive actually has the disease?

Question 21

How to calculate positive predictive value?

Answer 21

Those who are positive and tested positive over total people who are positive

Question 22

What is negative predictive value?

Answer 22

Proportion of people who are tested negative and actually don’t have the disease

Question 23

How to calculate negative predictive value?

Answer 23

People who tested negative and does not have the disease over total negatives