Chapter 11: Screening for Disease

Question 1

What is mass screening?

Answer 1

Also called pop. screening. Refers to the screening of total pop.groups on a large scale

Question 2

What is selective screening?

Answer 2

Also called targeted screening. Applied to subsets of the pop. at a high risk for disease or certain conditions as the result of family history, age, or previous exposures.

Question 3

What is screening?

Answer 3

examination of a group of usually asymptomatic individuals to detect those a high probability of having or developing a disease
-Secondary prevention

Question 4

Uses of screening?

Answer 4

• detect cases (to test in patients for cancer, etc.)
• control of disease
• research
• education

Question 5

What makes a good screening?

Answer 5

• Simple: easy to learn
• Rapid: quick to administer and get results
• Inexpensive: good cost ratio benefit
• Safe: no harm to participants
• Acceptable to target group

Question 6

Validity?

Answer 6

Accuracy
-the ability of a test to predict if a person has the disease or not; a true measure
Valeria was accurate about the test she performed on herself. She had Leukemia

Question 7

Reliability?

Answer 7

Precision. Consistency
-the ability of a test to give consistent results when performed more than once on the same person under the same conditions

Question 8

Types of validity?

Answer 8

• Content
• Criterion referenced
• Construct

Question 9

Measurement error?

Answer 9

constant errors introduced by a faculty measuring device and tend to reduce the reliability of measurements

Question 10

Halo Effect?

Answer 10

the influence upon an observation of the observer’s perception of the characteristics of the individual observed

Question 11

Social desirability effect?

Answer 11

Someone answers in a way that is agreeable w/ other people

Question 12

Sensitivity?

Answer 12

the ability of a test to correctly identify those w/ the disease or condition (true positives)
-high sensitivity

Question 13

Is there a difference between screening and diagnosis?

Answer 13

Yes. Screening tests evaluate an individual’s risk of developing a genetic condition, while diagnostic tests identify genetic conditions.

• Positive screening results are followed by diagnostic tests to confirm actual disease
• Screening is more of testing on an individual to see if there is a disease inside of them.

Question 14

Types of screening?

Answer 14

• Mass screening
• Selective screening
• Multiphasic screening

Question 15

Mass screening?

Answer 15

Screening on a large scale of total population groups, regardless of risk status, usually for research or surveillance purposes

Question 16

Selective screening?

Answer 16

Screening of selected groups of people in high risk categories

Question 17

Multiphasic screening?

Answer 17

Multiple screening tests together among a large group of people

Question 18

What are societal considerations of screening?

Answer 18

• Condition should be important to the individual and the community
• Favorable cost ratio benefit
• High public acceptance of the test

Question 19

Scientific considerations?

Answer 19

• Natural history of the condition should be understood properly
• A knowledge base is good for prevention and occurrence of disease

Question 20

Ethical considerations?

Answer 20

• The program can alter the natural history of the condition in a significant proportion of those screened
• Suitable, acceptable tests for screening and diagnosis of the condition are available
• Acceptable, effective methods of prevention are available

Question 21

Types of reliability?

Answer 21

• Repeated measurement
• Internal consistency
• Interjudge

Question 22

What is repeated measurement reliability?

Answer 22

the degree of consistency among repeated measurements of the same individual on more than 1 occasion

Question 23

What is internal consistency reliability?

Answer 23

evaluates the degree of agreement or homogeneity

within a questionnaire measure of an attitude, a personal characteristic, or a psychologic attribute

Question 24

What is interjudge reliability?

Answer 24

reliability assessments derived from agreement among trained experts

Question 25

What is content validity?

Answer 25

The degree to which the measurement incorporates the domain of the phenomenon under study

Question 26

What is criterion-referenced validity?

Answer 26

Found by correlating a measure with an external criterion of the entity being assessed

Question 27

What is construct validity?

Answer 27

Degree to which the measurement agrees with the theoretical concept being investigated

Question 28

Are validity and reliability direct or inverse?

Answer 28

Inversely proportional

-when one goes up, the other is down

Question 29

Sensitivity?

Answer 29

The ability of a test to correctly identify those with the disease or condition (true positives)
-Formula: a/a+c

Question 30

Specificity?

Answer 30

The ability of a test to correctly identify those without the disease or condition (true negatives)
-Formula: d/b+d

Question 31

What is PPV?

Answer 31

Positive Predictive Value; PV+. The probability of having the disease if you test positive.

• The proportion of people who screen + and truly have the disease
• a/(a+b)

Question 32

What is NPV?

Answer 32

Negative Predictive Value; PV-. The probability of not having the disease if you test negative.

• The proportion of people who screen - and truly do not have the disease
• d/(c+d)

Question 33

Prevalence=?

Answer 33

those who were screened who have the disease

-(a+c)/(a+b+c+d)

Question 34

Accuracy? (efficiency)

Answer 34

• those who were screened who received correct test results

- (a+d)/(a+b+c+d)

Question 35

If you have a fatal disease with no treatment (such as

Creutzfeldt-Jakob disease), optimize what? Why?

Answer 35

Specificity; b/c

Question 36

If you are screening to prevent transmission of a preventable disease (such as screening blood donors), optimize what? Why?

Answer 36

Sensitivity;

Question 37

Lead time bias?

Answer 37

The perception that the screen-detected case has longer survival because the disease was identified early

Question 38

Length bias?

Answer 38

Tumors identified by screening are slower growing and have a better prognosis.

Question 39

Selection bas?

Answer 39

Motivated participants have a different probability of disease than do those who refuse to
participate.