What is the difference between the quantitative FIT test (qFIT) and lateral flow at-home "FIT" tests?

A qFIT test is a "quantitative" analysis performed in a laboratory to quantify the amount of blood present in a stool sample. This is what the NHS and every other country uses for bowel cancer screening / testing. If this test demonstrates blood in the stool you would go for a colonoscopy.

In contrast, at-home "FIT" tests are a type of lateral flow test. They are not "quantitative" - i.e. they don't give a numeric result of the amount of blood in the stool. They are a similar technology to a COVID lateral flow test - you need to look for the presence or absence of a line on the cassette to read if the result is "positive" or "negative".

These devices are not suitable and should not be used:

• They tend to be less sensitive for the detection of blood than lab-based qFIT test.

• Reading the result is very prone to error - as you'll probably have experienced if you've ever squinted at a COVID lateral flow test trying to figure out if there is a line there or not. A lab based qFIT test gives you a number - there's no ambiguity.

• Most importantly, these tests have not been assessed for bowel cancer screening - i.e. we have no data from trials validating that they work. In contrast we have a lot of trial data validating the use of lab-based qFIT tests for bowel cancer screening.

• There's significant variation in quality from manufacturers with very little regulatory oversight. All lab-based testing in the UK is regulated by UKAS and standards have to be met. So you can have confidence that a qFIT test in a lab is the same whichever lab you use.

So all-in-all, lateral flow at-home "FIT" tests are not suitable for bowel cancer screening and you should not trust something as important as ruling out cancer to them.

The same concerns apply to lateral flow at-home "FIT" tests.