Around 4 in 100 people (4%) may initially receive an unclear result. This means that there was a hint of blood in the sample, but not enough to give an abnormal result. An unclear result can be caused by conditions such as piles (haemorrhoids). Having an unclear result doesn't mean you have bowel cancer: it simply means that the FOB test needs to be repeated. Most people who repeat the FOB test go on to receive a normal result.
You'll be sent a new FOB test kit. You should follow the instructions and return the samples as before.
If you have a second or third unclear FOB test, or an abnormal result, you'll be given an appointment to see a specialist screening practitioner. The appointment will be at your local hospital or screening centre and should be within a week of the letter telling you the FOB test result.
The practitioner will explain what your result means and answer your questions. They will discuss having a colonoscopy and give you a detailed explanation of the procedure, including its benefits and risks. They will also assess whether you're fit to have a colonoscopy.
A colonoscopy isn't appropriate for everyone. If you're not able to have one, you may be offered a different investigation, such as a CT colonography or barium enema.
If the result of your repeat test is normal, you may be sent another kit just to confirm the result. Other reasons you may be asked to repeat the FOB test are:
Sometimes there's a technical problem when your samples are tested in the laboratory. If this happens you'll be sent a letter and another test kit to collect more samples.
Sometimes the FOB kit can't be tested in the laboratory because it hasn't been used properly or has been damaged. If this happens you'll be sent a letter and a replacement kit.