What is a Galleri blood test? How cancer test works, who makes it, what price is it -  and is it FDA approved

Thousands of people are set to take part in an NHS trial for a simple blood test that can detect more than 50 types of cancer before symptoms appear.

But what is the Galleri test, how does it work, where is it currently available and how much does it cost?

Here’s what you need to know.

What is the Galleri blood test and how does it work?

The Galleri test can detect cancers that are not routinely screened for and can pinpoint where in the body the disease is coming from with a high degree of accuracy.

It works by looking for chemical changes in fragments of genetic code that leak from tumours into the bloodstream.

Some cancer tumours are known to shed DNA into the blood a long time before a person starts experiencing any symptoms.

All cells in your body release DNA into the bloodstream, but DNA from cancer cells is different from the DNA of healthy cells.

The Galleri test looks at the DNA in your blood in order to determine if any of it may have come from cancer cells, and the results can point to where in the body the cancer is coming from.

The Galleri is currently available in the US, where it has been recommended for people at higher risk of cancer, including the over-50s.

However, it does not detect all cancers and will not replace NHS screening programmes, such as those for breast, cervical and bowel cancer.

The Galleri blood test is made by a company called GRAIL and is not currently approved by the US Food and Drug Administration (FDA).

How effective is the Galleri test?

The test has been found to be particularly effective at finding cancers that can be difficult to identify early, such as head and neck, bowel, lung, pancreatic, and throat cancers.

Research published in the journal Annals of Oncology in June found that the test had a very low false positive rate, which means that very few people would be wrongly diagnosed with cancer.

Scientists analysed how the test worked in 2,823 people with the disease and 1,254 people without, correctly identifying cancer in 51.5% of cases across all stages of the disease, and wrongly detected cancer in just 0.5% of cases.

When it came to solid tumours that are not currently screened for, including oesophageal, liver and pancreatic cancers, the ability to generate a positive test result was twice as high (65.6%) as for solid tumours with screening options.

In regards to blood cancers, around 55% of cases were detected, while the test correctly identified the tissue in which the cancer was located in the body in 88.7% of cases.

How much does the Galleri test cost?

In the US, the cost of the Galleri test may vary depending on the practice setting and healthcare provider who orders your test. The list price for the Galleri test is currently $949.

The test is not currently available in the UK outside of clinical trials and it’s not yet been revealed how much it could cost the NHS.