Stool analysis

Question 1

Describe how the gFOBT test works

Answer 1

FOB test used to look for presence of gastrointestinal bleeding
•Positive test indicated by colour change on card to blue. Negative test will shoe no colour change
•Positive result indicates blood anywhere in GI tract or from piles, therefore not always an indication of colorectal cancer substances that can cause effect results:

Question 2

What can cause a positive result with gFOBT?

Answer 2

Blood
Ulcers, polyps, haemorrhoids, NSAIDS
NSAIDS can cause bleeding and lead to a false positive result 7 days before test
Red meats ( beef, lamb, liver) : Components of blood in the meat can cause a positive test result 3 days before testing
Vitamin C more than 250mg a day from supplements or citrus fruits and juices can affect chemicals in the test 3-7 days before test

Question 3

How does the FIT test work?

Answer 3

Uses antibodies that can recognise human haemoglobin, if human haemoglobin is present in the stool i.e. from GI bleeding it binds to the antibodies
Used to detect and quantify the amount of human blood in a single stool
Positive result -> (Faecal occult blood (FIT) >10 μg Hb/g faeces)
Only detects human blood from the lower intestines
Positive test can suggest bleeding in the GI tract that requires further investigation e.g colonoscopy

Question 4

What are the advantages of FIT vs GFOBT?

Answer 4

Less chance of false positives because the test is not influenced by the presence of other blood in the stool ie that ingested through the diet+ is More sensitive and specific
Fit only need 1 sample, no dietary changes
FIT is easier to use only 1 sample vs 3 for the gFOBt test
FIT has a sensitivity of 120 micrograms/g more sensitive and can detect signs of cancer earlier