A breakthrough advance that turns conventional wisdom on its head could lead to a simple blood test for Alzheimer's, research has shown.
The same technology, successfully tested on human patients, could make it easier to spot hard-to-detect cancers and other diseases.
It involves using synthetic molecules called peptoids to "fish" for disease-specific antibodies in the blood.
The approach turns the usual way of conducting blood tests on its head.
Traditionally, the tests work by detecting immune system antibodies that target natural proteins linked to diseases.
These proteins, known as "antigens", may be attached to viruses, bacteria and cancer cells, or be associated with brain diseases such as Alzheimer's and Parkinson's.
Previously, there has been no way of identifying disease-specific antibodies without first establishing what antigens trigger their production. This often proves an insurmountable obstacle.
The new technique gets around the problem by substituting artificial peptoids for antigens.
The molecules come in a wide range of different shapes, some of which happen to fit the sought after antibodies in much the same way as interlocking pieces of a jigsaw puzzle.
Peptoids that attract antibodies associated with certain diseases can act as markers for those conditions.
The team in La Jolla, California, pioneering the technology first tested the concept on mice with a condition resembling multiple sclerosis.
From a few thousand peptoids, the scientists hit on a handful that could distinguish blood samples taken from healthy and sick mice.
The researchers then applied the screening technique to six Alzheimer's patients, six Parkinson's disease patients and six healthy "control" individuals.
Three peptoids were identified that captured antibodies specific to Alzheimer's. In these patients they were present in at least three-fold higher levels than in either the Parkinson's or control groups.