Screening

Question 1

What are the positives of screening?

Answer 1

Identifies disease sooner
Improve patient outcome via treatment
Early diagnosis and treatment
Reduce risk of disease/complications

Question 2

What conditions are screened for in the UK?

Answer 2

AAA, bowel cancer, breast cancer, cervical cancer

Question 3

What four criteria must be met for approval for screening?

Answer 3

Disease/condition aspects
Test aspects
Treatment aspects
Programme aspects

Question 4

What are the disease aspects?

Answer 4

Important health problem
Understand epidemiology and natural Hx
Early to detect
Cost-effective intervention

Question 5

What are the test aspects?

Answer 5

Simple
Safe
Precise
Valid
Acceptable to patients
Know % of +ve/-ve test
Defined level of +ve cut off

Question 6

What are the treatment aspects?

Answer 6

Effective evidence-based treatment
Early treatment is advantageous
Policy on who to treat
Good availability of treatment

Question 7

What are the programme aspects?

Answer 7

Proven as effective
Counselling available
Diagnosis facilities

Question 8

Define diagnosis

Answer 8

A definitive identification of suspected disease by application of tests, exams or other extensive procedures to definitively label people as having a disease or not

Question 9

What are some general cons of screening?

Answer 9

Cause anxiety
Reduced QoL by treatment
Treating something that may not have caused problems
Drain resources
Risks of screening

Question 10

What is sensitivity?

Answer 10

Good at detection (out of disease present, how many have it)

Question 11

What is specificity?

Answer 11

Good at showing well people are well (out of disease absent, how many test negative)

Question 12

What is positive predictive value?

Answer 12

If have positive test, how likely is it that they have disease

Question 13

What is negative predictive value?

Answer 13

If have negative test, how likely is it they don’t have the disease

Question 14

How will sensitivity, specificity, PPV and NPV be affected by population size or prevalence?

Answer 14

Sensitivity and specificity are values of test so unaffected

Low prevalence -> low PPV as lots of false +ves

Question 15

What are false positives and negatives?

Answer 15

False +ve is a +ve test but person doesn’t have disease

False -ve is a -ve test but person does have disease

Question 16

What are the rules for working out equations?

Answer 16

Always have true positive or negative on top
Whatever was on top line must be on bottom
Bottom line must have true and false on it
PPV has all positives in it so true pos/true pos plus false pos
NPV has all negatives in it

Question 17

Give three types of bias that can occur in screening

Answer 17

Lead time: find disease earlier so looks like you prolonged life but actually just prolonged how long you know about it

Length time: find slow progressing diseases that were unlikely to cause a problem

Selection: people who care more about their health are more likely to go for screening even though they are more likely to be healthy

Question 18

Define screening

Answer 18

A systematic attempt to detect an unrecognised condition by application of tests, exams or other procedures which can be rapidly applied to distinguish if apparently well people have a disease or not

Quick and cheap test-> screen +ve/-ve -> high/low risk -> tests

Question 19

What are the five main issues of screening?

Answer 19

Alters patient-doctor contact
Complexity of screening programmes
Evaluating screening programmes
Limitations of screening
Sociological critiques of screening

Question 20

What are the limitations of screening?

Answer 20

Potential for error so false +ve/-ve cause anxiety or complacency
GPs paid to do screening
Over-diagnosis

Question 21

What are the sociological critiques of screening?

Answer 21

Structural: patients responsibility so someone with mental illness may be unable to participate
Surveillance: always being watched and controlled
Social constructionist: non attendance=deviant
Feminist: more targeted to men than women