What is a faecal occult blood test?

Has your doctor recommended you have a faecal occult blood test to see if there’s blood in your stools? This test is used to diagnose bleeding disorders in your gut, including screening for early colon cancer. Get the lowdown here.

There are several medical conditions that may cause rectal bleeding, from haemorrhoids and gastro-enteritis to polyps and colon cancer (or bowel and colorectal cancer). Heavy bleeding in your gut is obvious, as it will show up in your faeces – and it should see you consulting your doctor immediately.

However, there is blood that may be present in your stools that isn’t visible to the naked eye and can’t be seen in your stools, in the toilet or on toilet paper. This is called occult blood and it will need a faecal occult blood test to detect it, says Dr Philippus Nel (Jnr), a general surgeon at Mediclinic Kloof in Pretoria.

‘A test for occult blood in the faeces is an indirect stool sample-based test that can detect colonic neoplasms or tumours,’ he explains. ‘There are two types of faecal occult blood tests available: the gauaic-based faecal occult blood test (gFOBT) and the faecal immunochemical-based test (FIT), which outperforms the gFOBT in terms of sensitivity. Both are used as screening tools for colon cancer detection and prevention.’

When are faecal occult blood tests recommended?

There are two scenarios when it comes to the use of these tests. You may have symptoms that prompt them, such as vague intermittent abdominal pain, weight loss, sensation of bloating, nausea and/or vomiting, and fatigue with or without cardiac symptoms, explains Dr Nel.

Alternatively, you may have no symptoms at all, but your doctor may recommend an age-appropriate colon cancer screening during a routine check-up. ‘These tests help screen the average risk patient (anyone older than 50 years, with no personal history of colorectal cancer or polyps, no family history of colorectal cancer and no history of inflammatory bowel disease) for colon cancer,’ Dr Nel says.

It’s a vital screening tool, considering that colon cancer is the fourth most common cancer diagnosed after prostate, lung and breast cancer, says Dr Nel. ‘Colon cancer incidence in southern Africa is four new cases per 100 000, with no difference in sex, according to the Cancer Association of South Africa. Colon cancer is most commonly diagnosed between 60 and 70 years old,’ he adds.

How is the faecal occult blood test performed?

You’ll be asked to give a small sample of your faeces which will be sent to an accredited laboratory for analysis. When prepping for this test, you don’t have to follow a restrictive diet but high vitamin C intake (more than 250 mg a day) should be avoided, advises Dr Nel.

Sometimes your family physician may do a rectal examination and an in-room occult stool test, but generally more than one sample needs to be taken and sent to a lab, explains Dr Nel. ‘For the FIT test, only one sample is needed, while the gFOBT needs three consecutive stool samples. The FIT is a more accurate screening option. There may be false positive results and false negative results with the gFOBT.’

The sample should reach the lab on the same day and, depending on the laboratory turnover, your test results should be available the next day.

It’s important to note that a positive result does not mean you have cancer, cautions Dr Nel. ‘The faecal occult blood test is a screening tool only and all positive screening tests have to be followed up with a colonoscopy to confirm a diagnosis.’