screening - core reading

Question 1

when is mass screening useful

Answer 1

exposure is common in the whole population

aims to shift the population distribution

Question 2

strength of population screening

Answer 2

• Equitable, targeting all those exposed even those at lower risk.
• Can get high coverage.
• Can be cost-effective.

Question 3

weakness of population screening

Answer 3

• Medicalization (e.g. widespread use of statins).
• Less acceptable to the individual
• Risk of over-treatment.
• Expensive

Question 4

strengths of high risk testing

Answer 4

• Effective (high motivation).
• Efficient.
• Acceptable.
• Easy to evaluate.

Question 5

weaknesses

Answer 5

Inequitable (misses a large amount of disease).
• Medicalization.
• Damage limitation as disease process already advanced.
• Can be hard to change individual behaviours.

Question 6

describe the prevention paradox

Answer 6

many people with small risk = more disease than few with a high risk
many people get small benefit - total benefit large
individual inconvenience high

Question 7

screening definition

Answer 7

test apparently healthy individuals - detect unrecognised disease/its precursers
so measures can be taken to prevent development or improve prognosis

Question 8

population in screening V diagnostic

Answer 8

s - healthy

d - symptomatic

Question 9

objective in screening V diagnostic

Answer 9

s - distinguish high and low risk

d - definite diagnosis

Question 10

describtion in screening V diagnostic

Answer 10

s - Relatively cheap, simple, and non-invasive

d - more expensive, complex and invasive

Question 11

ideal parameters in screening V diagnostic

Answer 11

s - sensitive, specific, may trade specificity for sensitivity
d - both high sensitivity and specificity - multiple investigations

Question 12

communicating results of screening tests

Answer 12

people think +ve test means they have disease, on reality low specificity

Question 13

potential harm to the individual

Answer 13

• False alarms which induce anxiety.
• Treatment of early disease, including potential side effects, even though the disease may not have progressed.
• Unnecessary investigations, including some invasive procedures.
• False reassurance if cases are missed.

Question 14

potential harm to the population

Answer 14

• Waste of resources that could be used elsewhere.
• Overall could produce more harm than good through over-treatment.
• Undermine primary prevention programmes if those who test negative feel they have ‘escaped’ disease and can continue risky behaviours (e.g. HIV and cholesterol testing).

Question 15

method for evaluating screening

Answer 15

obs studies - mortality +/ morbidity compared before and after screening/ screened compared with unscreened
hard to interpret - bias and confounding factors
economic analysis - need to look at effectiveness
mathematical modelling - predict impact of screening, used in infectious disease and cancer

Question 16

antenatal screening

Answer 16

downs - serum screening, nuchal thickness
anomalies - ultrasound 
sickle cell/thalassemia - blood tests 
Syphilis HIV, hepatitis B, rubella - 
Blood tests

Question 17

newborn screening tests

Answer 17

hearing - otoacoustic emissions
Sickle cell, cystic fibrosis, phenylketonuria, hypothyroidism -
Dried blood spot on Guthrie card
anomaly - physical examination

Question 18

school children

Answer 18

Hearing, vision, height, weight, developmental milestones - examination by health visitor

Question 19

<25

Answer 19

chlamydia - Nucleic acid amplification test from urine or genital swab

Question 20

25 -64

Answer 20

cervical cancer - cervical cytology

Question 21

50 - 70

Answer 21

breast cancer - mammography every 3 yrs