A simple blood test to detect cancer early on? Israeli researchers believe they have developed one.

The test uses infrared light to detect miniscule changes in the blood of a person who has a cancerous growth somewhere, even before the disease has spread. Various molecules released into the bloodstream cause it to absorb infrared light slightly differently, compared to that of healthy people.

A spectrum of infrared light is beamed through the blood, placed on a surface, and interpreted by a mathematical formula, explained Professor Joseph Kapelushnik, of Ben-Gurion University and the Soroka Medical Centre in the desert city of Beersheba, south of Tel Aviv.

The test was tried on 200 cancer patients who had just been diagnosed and successfully detected the disease in some 90 per cent of them. It did not mistakenly detect cancer in dozens of healthy volunteers.

'When does a person usually go to the doctor? When he doesn't feel well. We want to detect it when the person still feels good,' the hemato-oncologist told dpa.

Kapelushnik, who conducts the research with several other scientists from the university and hospital in Beersheba, said the team hopes to start clinical trials in 18 months to two years.