A simple blood test can detect early stage liver cancer and more accurately diagnose a disease that is a major killer in Asia and Africa, researchers said on Wednesday.

Current tests include biopsies, imaging and the so-called AFP test in which doctors can detect malignant tumours based on the concentration of particular substances -- called markers -- in the blood.

But those methods are not as sensitive as the new test that can also indicate whether a tumour is in the early or latter stages and offers patients a better chance of survival, said Chitty Chen, of the Flanders Institute for Biotechnology and Ghent University in Belgium, who led the study.

"When you have liver cancer you do not have symptoms in the early stages," Chen said in a telephone interview. "Once you have symptoms your liver dysfunctions and it is often too late for treatment."

Liver cancer kills nearly 700,000 people each year, mainly in Africa and Asia which have a high prevalence of hepatitis infections that cause the disease.

In the study, published in the journal Hepatology, the researchers developed a blood test to detect changes in sugars attached to proteins that occur in liver cancer, Chen said.

The researchers also showed they could determine the size of the tumour based on the amount of two particular sugar groups that appeared in the proteins, she said.

Used with the AFP test, the new method was more accurate and can better detect liver cancer and save lives by getting patients earlier treatment, she added.