Los Angeles, July 16 -- Scientists are closing in on a long-sought goal - a blood test to screen people for possible signs of Alzheimer's disease and other forms of dementia.

On Monday at the Alzheimer's Association International Conference, half a dozen research groups gave new results on various experimental tests, including one that seems 88% accurate at indicating Alzheimer's risk.

Doctors are hoping for something to use during routine exams, where most dementia symptoms are evaluated, to gauge who needs more extensive testing. Current tools such as brain scans and spinal fluid tests are too expensive or impractical for regular check-ups.

"We need something quicker and dirtier. It doesn't have to be perfect" to be useful for screen...