Screening programmes

Question 1

Three cancer screening programmes delivered by the NHS

Answer 1

Bowel cancer

Breast cancer

Cervical cancer

Question 2

Conditions that make it possible for cancers to be screened

Answer 2

Common cancer

In an asymptomatic but identifiable population

Identifiable premalignant conditions

That can be treated to reduce mortality and morbidity

Question 3

Who is screening intended for?

Answer 3

People without symptoms

Question 4

Which organisations coordinate these screening programmes?

Answer 4

National Office of the NHS Cancer Screening Programmes

Question 5

Who receives bowel cancer screening kits?

Answer 5

Incidences increase after 50 years of age

If registered with GP, will automatically receive kits if aged 60-74

Question 6

What does the bowel cancer screening kit contain?

Answer 6

A prepaid return envelope

An orange and white cardboard test kit

6 cardboard sticks to collect stool samples

Instructions and information leaflet

Question 7

How does the faecal occult test work?

Answer 7

Collect stool samples on 3 different days

Samples collected with cardboard sticks and transferred to collection kit

Kit is then posted back in a prepaid envelope

Should be received at the pathology laboratory at a screening centre within 14 days

Question 8

Within how many days should the faecal occult blood test be received at the pathology laboratory at a screening centre?

Answer 8

Within 14 days

Question 9

What does the FOBT test for?

Answer 9

Detect hidden blood in the stool

Could be indication of pre-malignant condition or cancer

Question 10

How are the FOBT analysed?

Answer 10

By a manual qualitative process

Question 11

What type of FOBT does the NHS use?

Answer 11

Guaiac-based FOBT

Question 12

What does the kit of the guaiac-based FOBT consist of?

Answer 12

2 paper squares in 3 flaps impregnated with a colourless substance called guaiaconic acid

Question 13

What happens chemically in the guaiac-based FOBT?

Answer 13

Developing solution containing hydrogen peroxide is added

If there is occult blood in the sample, a guaiac-peroxidase reaction occurs

Colour change from colourless -> blue-green colour within 30 to 60 seconds

Question 14

What causes the colour change in the guaiac-based FOBT?

Answer 14

Colour change happens because the heme-portion of haemoglobin in red blood cells has peroxidase activity

Peroxidase activity catalyses the oxidation of the colourless gluconic acid by hydrogen peroxide

Question 15

Why is the peroxidase activity of Hb termed pseudoperoxidase?

Answer 15

Haemoglobin is not a true peroxidase enzyme

Question 16

What causes the colour change in FOBT?

Answer 16

Hydrogen peroxide produces a blue quinone compound

Question 17

How should a patient prepare for the FOBT?

Answer 17

Avoid certain medications

Follow dietary restrictions for several days before collecting the stool sample

Question 18

What dietary restrictions must patients follow before undergoing FOBT?

Answer 18

Avoid food with high peroxidase activity

Red meat 
Horseradish 
Broccoli 
Turnips 
Vitamin C supplements - high ascorbic acid activity 

Could give false positives

Question 19

What is the advantage of the Faecal Immunochemical Test?

Answer 19

Uses antibodies to globin to identify the presence of blood

The patients must not go under any dietary restrictions

Charity Beating Bowel Cancer has urged Public Health England that this is better option

Question 20

What is a normal result in FOBT?

Answer 20

None of the 6 windows show colour change

Question 21

What is an abnormal result in FOBT?

Answer 21

5-6 positive windows

Requires further investigation

Colonoscopy recommended

Question 22

What is an unclear result in FOBT?

Answer 22

1-4 positive windows

Second kit is sent out

If the second kit is normal, a third kit is sent out

If the second or third kit show 1+ positive spots = weak positive

Colonoscopy recommended

If both subsequent kits are normal then the result is normal

Question 23

What is sensitivity?

Answer 23

Proportion of individuals with the disease who are correctly identified by the test as positive

Question 24

What is the sensitivity of the FOBT?

Answer 24

55-92%

Since presence of blood in the stool does not necessarily mean colon cancer

Question 25

What is specificity?

Answer 25

Proportion of individuals without the disease who are correctly identified as negative

Question 26

What are the next steps for when FOBT detects blood in the stool?

Answer 26

Further investigation is needed, this usually consists of colonoscopy

People with abnormal results are offered an appointment or phone call with a specialist nurse

Question 27

What does the specialist nurse explain before the patient undergoes a colonoscopy?

Answer 27

The possible implication of the abnormal screening test result

What a colonoscopy involves

Assess the patient’s fitness for the procedure

Answer any question

Question 28

What is the specificity of the FOBT?

Answer 28

95%