Screening

Question 1

What is screening?

Answer 1

A presumptive idenitification of unrecognised disease by the application of tests which can rapidly sort out wel persons who probably have disease from those who do not

Question 2

What factors about the disease make a screening test worthwhile?

Answer 2

Known aetiology and risk factors (allows particular sub populations to be selected)

Known natural history (must have an asymptomatic period as screening must occur before disease process has begun)

High incidence and prevalence

High morbidity and mortality

Question 3

What factors of the test make a screening programme worthwhile?

Answer 3

Simple
Acceptable
Reliable
Valid

Question 4

What is sensitivity?

Answer 4

The probability that the test will be positive if the person has the disease

Question 5

What is specificity?

Answer 5

The probability that the test will be negative if the person does not have the disease

Question 6

What is positive predictive value?

Answer 6

The probability that the person has the disease if the test is positive

Question 7

What is negative predictive value?

Answer 7

The probability that the person does not have the disease if the test is negative

Question 8

What is positive likelihood ratio

Answer 8

The higher the better, more true positives and less false positives

Sensitivity/ 1-specificty

Question 9

What is negative likelihood ratio?

Answer 9

The ratio of true negatives vs false negatives

1-sensitivity/ specificity

Question 10

What factors of the treatment of a disease make the screening test worthwhile?

Answer 10

Available
Acceptable
Effective
Benefits from early detection- be aware of lead time bias

Question 11

What factors of the programme make a screening programme worthwhile?

Answer 11

Cost effective
Agreed protocol
Quality assurance
Does more good than harm