Screening

Question 1

Define screening

Answer 1

Screening is a procedure, test or examination to detect the presence of a disease among apparently healthy individuals.

Question 2

List the Usefulness of screening

Answer 2

1. Early detection
2. Early intervention
3. Better prognosis
4. Educative purposes
5. Research purposes
6. Treatment/preventive purposes

Question 3

What are the criteria for screening?

Answer 3

1. Natural hx of the dx must be known.
2. Disease must be of public health importance (i.e, have high prevalence, high mortality and reduces economic production)
3. There must be available treatment for the disease
4. Test must be acceptable
5. Test must be reproducible
6. Test must be cost effective
7. Test must be valid.
8. Disease must have a latent period

Question 4

Differentiate between sensitivity and specificity.

Answer 4

Sensitivity is the ability of a test to detect those who truly have the disease.

Sensitivity = true positive divided by total no.of people with the disease X 100%

Specificity - ability of a test to detect those who truly do not have the disease.

Specificity = true negative divided by total no.of people who do not have the disease X 100%

Question 5

Differentiate between positive and negative predictive value.

Answer 5

PPV - those that are positive to the disease truly have the disease and vice versa.

Question 6

Causes of non reliability of a test

Answer 6

Faulty equipment
Inter/intra observer variation
Biological variation.

Question 7

What is lead time?

Answer 7

Duration between detection of disease (via screening) and its usual clinical presentation and diagnosis.