Researchers in Japan and Australia say they have made progressin developing a blood test that could one dayhelp doctors identify who might get Alzheimer's disease.The scientists said the test can recognize a protein known as amyloid beta,which other studies have linked to Alzheimer's.They said it was correct more than 90 percent of the timein a study involving over 370 people.The findings were published in the journal Nature.Alzheimer's disease is the most common form of dementia.Experts believe dementia affects close to 50-million people worldwide.By the year 2050, it is expected to affect more than 131 million people.Those numbers come from Alzheimer's Disease International, a non-profit group.Currently, doctors have two ways to identify a buildup of amyloid beta in the brain.One is a brain scan or brain imaging;the other is invasive cerebrospinal fluid testing,also known as a spinal tap.But both tests are invasive, costlyand may only show results when the disease has already started to progress.There is no treatment that can slow the progression of Alzheimer's.Current drugs can only ease some of the effects of the disease.Having a simple, low-cost blood test could make it easierfor drug companies to find enough people who are at riskof developing Alzheimer's to test new medicines, said Katsuhiko Yanagisawa.He was one of the leaders of the study.He works at the Japanese National Center for Geriatrics and Gerontology.Alzheimer's disease is thought to start developingyears before patients have any signs of memory loss.Experts say an important factor in finding an effective treatmentwill be the ability to recognize signs of the disease early."You have got to walk before you run," said Colin Masters,a co-leader of the study and a professor at the University of Melbourne in Australia."You have to learn to diagnose the disease directlybefore you can hope to see the effect of therapeutic intervention.And that's where the real value in this test will come," Masters added.The study involved 252 Australian and 121 Japanese patients.They were all between 60 and 90 years old.Scientists not directly involved in the study said it made an important step,but now the findings need to be confirmed.Mark Dallas is a teacher at Britain's University of Reading.He said, "if (it) can be repeated in a larger number of people,this test will give us an insight into changes occurring in the brainthat relate to Alzheimer's disease."Abdul Hye works at King's College London's Instituteof Psychiatry, Psychology & Neuroscience.He said the blood test was still a long way from being able to be used in medical centers.John Hardy is a professor of neuroscience at University College London.He said it was a "hopeful study," one that could improve diagnostic accuracy.