By Maggie Fox

 WASHINGTON (Reuters) – New tests involving blood and brain scans can detect symptoms of Alzheimer’s disease, and brief appraisals of real-life functioning can predict who is likely to develop it.

 The tests will be critical, experts told a meeting on Alzheimer’s disease, because more than 26 million people now have Alzheimer’s disease and this number will quadruple, to 106 million, by 2050.

 "By 2050, 1 in 85 persons worldwide will have Alzheimer’s disease," said Ron Brookmeyer of Johns Hopkins University, who led the study on how many people have the disease.

 Anders Lonneborg and colleagues of DiaGenic, a biotech company based in Oslo, Norway, found a set of 96 genes that are expressed differently in Alzheimer’s compared with healthy people.

 Their study of more than 100 older people, half from memory clinics and half from senior centers, identified Alzheimer’s accurately 85% of the time.

 The company has applied to regulators in the United States and Europe to approve the test, Lonneborg told a meeting of the Alzheimer’s Association in Washington.

Brain Scans

 Christos Davatzikos and colleagues at the University of Pennsylvania used a combination of PET and MRI scans to diagnose incipient Alzheimer’s disease.

 This method correctly found all 15 cases of mild cognitive impairment and cleared 15 healthy volunteers. "This abnormal pattern of brain structure and blood flow detected not only mild cognitive impairment but even earlier… when they were clinically normal," Davatzikos told the news conference.

Other Screening Approaches

 Deborah Barnes and colleagues at the University of California San Francisco developed a more low-tech approach. Their study followed 3,300 elderly people for 6 years to see what factors best predicted who would begin to develop Alzheimer’s.

 A combination of a few simple measures worked best. They included greater age, scores on a simplified version of a standard cognitive exam, the time it took to button a shirt and the time needed to walk 15 feet (5 metres), being underweight, and not drinking any alcohol at all.

 Another study underscored the value of watching someone’s weight. Dr. James Mortimer of the University of South Florida in Tampa and colleagues have been studying 678 Catholic nuns who have agreed to be studied through their lives and who have donated their brains for research after death.

 The nuns who suddenly lost weight were far more likely to develop Alzheimer’s. In fact, even nuns who were never diagnosed with Alzheimer’s were found to have the disease after they died, Mortimer said.

 "Unexplained weight loss in non-demented older people may be a very useful early symptom of disease," Mortimer said.