'Ingenious' new lung cancer blood test

A new test for the early detection of lung cancer is to be tested in a trial in Scotland involving 10,000 smokers.

The test was developed at Nottingham University and the company that now make it say it can detect cancer up to five years sooner than conventional tests like X-rays.

The science behind the test is ingenious.Your body is very good at spotting cancer cells in the early stages - and it produces antibodies to attack them, just like bacteria or viruses.

There may be very few cancer cells but lots of antibodies - they're easier to detect. You're not looking for a needle in a haystack, you're looking for the haystack.

But whether the test will work as a screening test, we don't yet know.

A good screening test needs to do two things - obviously to spot as many cancers as possible - this test detects about 40%. Now that's not brilliant but its better than nothing.

The second thing you need is a test that doesn't set off false alarms - doesn't say you've got cancer when you haven't really. The company selling this test says its false positive rate is about 7%.

The trial in Scotland will show how those figures work out in practice - and whether using the new test in screening will be economic.