A magnetic wire could revolutionise blood tests for cancer.

Blood tests are seen as the future for cancer detection, catching the disease early by picking up cells from tumours in the bloodstream.

However, there are so few of these cells that a regular blood sample may contain none.

Now US scientists have the answer in the form of a magnetised wire which attracts tumour cells. Researchers at Stanford University found they can inject magnetic nano- particles containing an antibody which clings to the cells from tumours.

Blood tests allow doctors to target cancers based on their genetic make-up, which differs between patients.

They pick up circulating tumour cells which escape into the blood but are often scarce.

The technique, which involves threading a magnetic wire into a vein, can attract up to 80 times more cancer cells than current methods.

So far tested only in pigs, it is hoped human trials will follow soon, according to the journal Nature Biomedical Engineering.

Co-author Dr Sam Gambhir, professor of radiology at Stanford’s school of medicine, said: “It would take about 80 tubes of blood to match what the wire is able to sample in 20 minutes.

“We’re hoping this approach will give us better insight into just how rare these circulating tumour cells are, and how early on they exist," Gambhir said.