Australian and Japanese scientists have developed the world's first blood test that has the potential to accurately identify people at risk of developing Alzheimer's disease up to 30 years before full-blown symptoms emerge.

The discovery could rapidly speed up the progress of clinical drug trials to treat the disease and could eventually form the basis for routinely screening for and diagnosing Alzheimer's disease in the community.

The research teams found they were able to detect a specific peptide in the blood, a biomarker for the build-up of the protein amyloid beta in the brain; a fundamental hallmark of Alzheimer's disease.

The blood test used a highly specialised and sensitive mass spectrometry technique to measure extremely low concentrations of the peptide in the blood plasma samples of two patient groups: 252 Australians and 121 in a Japanese group.