M101 Public Health Screening

Question 1

What are the three different levels of prevention?

Answer 1

Primary – preventing onset of disease
Secondary – preventing progression of disease (early diagnosis and treatment)
Tertiary – reducing disability and suffering from disease

Question 2

What percentage of cancers can be prevented by not smoking?

Answer 2

at least 40%

Question 3

How is HbA1c measured?

Answer 3

a sample of blood will be taken, usually from the arm.

Question 4

What is the purpose of screening tests?

Answer 4

they sort out apparently well persons who probably have a disease from those who probably do not

Question 5

What data might screening identify?

Answer 5

risk factors, genetic predisposition / susceptibility, and precursors, or early evidence of disease

Question 6

What are the aims of screening tests?

Answer 6

Better prognosis / outcome for individual
Protect community from contagious disease
To select out unhealthy/unfit people (for certain jobs)
Selection of healthy individuals
Rational – more efficient allocation of resources
Research (e.g. on natural history of disease)

Question 7

What are the different types of screening?

Answer 7

Mass or population
Multiple or multiphasic
Targeted
Case-finding or opportunistic

Question 8

What happens during mass or population screening?

Answer 8

screening of the whole population (cancer)

Question 9

What happens during multiple or multiphasic screening?

Answer 9

the use of two or more screening tests (to detect two or more diseases) on the same occasion (diabetes, hypertension)

Question 10

What does targeted screening involve?

Answer 10

the screening of groups with specific exposures (HIV, HBV, HCV)

Question 11

What does case-finding or opportunistic screening involve?

Answer 11

screening patients who consult a health practitioner for some other purpose (Chlamydia)

Question 12

What are the WHO criteria for population-based screening otherwise known as?

Answer 12

the Wilson and Junger criteria

Question 13

What are the medical WHO criteria for population-based screening?

Answer 13

the condition should be an important health problem
the natural history of the disease should be adequately understood
there should be a recognizable latent or early symptomatic stage
there should be a safe, suitable and acceptable screening test or examination

Question 14

What are the political WHO criteria for population-based screening?

Answer 14

test must be quick / easy to administer /

non-invasive / inexpensive

Question 15

What are the healthcare system WHO criteria for population-based screening?

Answer 15

facilities for confirming the diagnosis and follow-up should be available
there should be an accepted treatment or effective intervention for patients with recognized disease
there should be an agreed policy on whom to treat
treatment started at an early stage should be of more benefit than treatment started later
the cost of case-finding (including test/diagnosis/treatment) should be economically balanced in relation to possible expenditure on medical care as a whole
case finding should be a continuing process and not a ‘once for all’ project

Question 16

What is the NHS policy on breast cancer screening?

Answer 16

women aged 50-70 years invited once every 3 years (women >70 can request/self-refer)

Question 17

What is the NHS policy on cervical cancer screening?

Answer 17

all women aged 25-64 years (to check the health of cells in the cervix)
25-49 years invited once every 3 years, and those aged 50-64 invited every 5 years

Question 18

What is the NHS policy on bowel cancer screening?

Answer 18

faecal occult blood test for persons aged 60-74 years every 2 years (home screening kit)

Question 19

What is the NHS policy on abdominal aortic aneurysm screening?

Answer 19

is offered to all men in their 65th year of age

men over 65 can self-refer

Question 20

What two conditions are all neonates screened for?

Answer 20

phenylketonuria

congenital hypothyroidism

Question 21

What is the NHS policy on the elderly for general check ups?

Answer 21

patients aged ≥75 years have a general assessment every 12 months

Question 22

What is the NHS policy on cardiovascular risk factor screening?

Answer 22

newly registered patients and patients not seen within 3 years

Question 23

What is the NHS policy on bladder cancer screening?

Answer 23

for those with occupational exposure

Question 24

What is the NHS policy on HIV screening?

Answer 24

all women receiving antenatal care

Question 25

What features should a good screening test have?

Answer 25

high sensitivity
high specificity
high PVP

Question 26

What type of test should have high sensitivity?

Answer 26

a screening test which is used to rule out (discard) a diagnosis

Question 27

What type of screening test should have high specificity?

Answer 27

a confirmatory test which is used to rule in (confirm) a diagnosis

Question 28

What two important clinical questions are not directly answered by sensitivity and specificity tests?

Answer 28

If a patient’s test result is +ve, what is the probability that they have the disease?
If a patient’s test result is -ve, what is the probability that they do not have the disease?

Question 29

What is Predictive value +ve influenced by?

Answer 29

the sensitivity / specificity of the screening test and by the prevalence of the detectable preclinical phase in the screened population

Question 30

What is Predictive value +ve more influenced by?

Answer 30

specificity bc the specificity determines the no. of false-positive results

Question 31

What does a low PVP imply?

Answer 31

that resources are being wasted on diagnostic follow-ups of false-positive patients