Cancerbackup: The FOB test

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The faecal occult blood (FOB) test


About the test

The faecal occult blood (FOB) test is a way of detecting tiny amounts of 'hidden' blood in your bowel motions. The test doesn’t tell you if you have bowel cancer, or a polyp, but if there is blood in your bowel motions you may be offered further investigations of your bowel to find out the cause of the bleeding. You may have to repeat the FOB test or have an examination of your bowel (a colonoscopy).

Screening may not be appropriate for you if you:

  • have had bowel investigations (such as a colonoscopy or barium enema) in the last two years
  • are being treated for bowel cancer
  • have had your large bowel removed
  • are being treated for Crohn’s disease or ulcerative colitis
  • are on a bowel polyp surveillance programme
  • are waiting bowel investigations that have been arranged by your GP.

If you are sent an FOB test kit and you aren’t sure whether you should do the test or not, you should ring the Freephone helpline number, which is on the letter that comes with the test.

You don’t have to take part in the bowel cancer screening programme. If you do not want to take part you can choose simply to not complete and return the FOB test kit, or you can contact the Freephone number on the letter to let the programme know that you don’t want to participate.


The FOB test kit

After you have received a letter inviting you to take part in the bowel cancer screening programme, you will be sent an FOB test kit and instructions, which you use in the privacy of your own home. The kit includes:

  • full instructions
  • six cardboard sticks to collect the samples
  • an orange and white test card
  • a prepaid hygienic envelope to return the samples.

Example of a testing card
Example of a testing card

There are three parts to the test for three separate bowel motions.

Doing the test

Before collecting each bowel motion it's a good idea to get everything ready. You will need to have two of the supplied cardboard sticks and the orange and white test card. Write the date on the first flap on the test card, then peel back the flap. Underneath you will see two windows – one for each sample of your bowel motion.

Collecting your samples

It's important that the bowel motion you use to collect your sample from has not been in the toilet bowl, as this can affect the result of the test. You can collect the bowel motion in a clean disposable plastic container (such as a cleaned margarine or ice cream tub), in your hand covered in a plastic bag, or in some folded toilet paper.

Once you have collected your bowel motion, use one of the cardboard sticks to take a small piece. Spread it thinly over the first window. Use the second cardboard stick to collect a sample from a different area of your bowel motion. Spread it thinly over the second window.

Once you have completed both windows, seal the flap on the test card. The cardboard sticks should be wiped with toilet paper, wrapped up and thrown away in an outside bin. They shouldn’t be flushed down the toilet.

The second and third samples are collected in the same way, using the two windows under flap two and then flap three. The three samples need to be taken from three different bowel motions, but they don’t have to be collected from three in a row. It's important that all the samples are collected and the kit returned within 14 days of the first sample.

Once you have all three samples you can send the kit to be tested using the prepaid hygienic envelope.

If you have any questions about the sample collection, or if you need a new testing kit to start again, you can ring the Freephone helpline number. The number will be printed on the kit instructions.

If you don’t return the testing kit you will be sent a reminder after about four weeks. If you have decided not to participate in the screening programme, you can either ignore the reminder, or contact the Freephone helpline to tell them you won’t be sending your kit back.


Content last reviewed: 01 April 2008
Page last modified: 14 January 2009

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