According to a new study in the Journal of the American Medical Association, certain proteins found in cerebrospinal fluid may accurately identify the people with mild cognitive impairment who are most likely to develop Alzheimer's disease.

The scientists could identify people at greatest risk by testing for a shortage of a sticky compound called amyloid-beta in the spinal fluid and for excess amounts of two kinds of a protein called tau.

Dr. Niklas Mattsson, from the Institute of Neuroscience and Physiology, Clinical Neurochemistry Laboratory at Sahlgrenska University Hospital in Molndal, Sweden and lead researcher said, "We confirmed, in a large multi-center study, that proteins in cerebrospinal fluid identify early-stage Alzheimer's disease, as suggested by previous smaller studies."

"These proteins may be used in research, in particular in drug trials, and also as a complement to clinical diagnostics, in particular when disease-modifying drugs become available," he said.

It has been difficult predict who is likely to get Alzheimer’s disease as its early symptoms are often mistaken for routine cognitive losses caused by aging.

In the study Mattsson's team studied the accuracy of using three biomarkers found in spinal fluid in predicting Alzheimer's diseases which are beta-amyloid1-42 (Aß42), total tau protein (T-tau), and tau phosphorylated at position threonine 181 (P-tau).

750 people with mild cognitive impairment, 529 people with Alzheimer's disease and 304 healthy people were tested for these biomarkers. Each volunteer underwent a spinal puncture and contributed a cerebrospinal fluid sample. After two years, 271 of those with mild cognitive impairment progressed to Alzheimer's disease and 59 developed other dementias.

People who developed Alzheimer's had lower levels of Aß42 and higher levels of P-tau and T-tau compared with patients with mild cognitive impairment who did not develop Alzheimer's reported the researchers.

"The cerebrospinal fluid proteins Aß42, T-tau, and P-tau are useful in diagnosis of early-stage Alzheimer's disease," Mattsson noted.

Mattsson said roughly half of all elderly people with mild cognitive impairments later develop Alzheimer’s disease, and the drugs currently available treat only Alzheimer’s symptoms, not the disease. “It’s very important to interfere with the disease as early as possible, and this is where the diagnostic test comes in.” Screening for changes in amyloid-beta and tau in drug trial participants might also indicate which medications are thwarting the disease process, Mattsson said.

Maria Carrillo, director of medical and scientific relations at the Alzheimer's Association said, "We are very excited that cerebrospinal fluid biomarkers are holding up in terms of their specificity and sensitivity in diagnosing the disease early. The next step is to make sure these tests are standardized so that the test will mean the same thing, no matter where it is taken."

If these tests are standardized, it could be a biomarker that identifies the disease, Carrillo said. "If over the next two or three years we also have a therapy, then we need to examine how that therapy works in an incipient form of Alzheimer's, not once those memories have already started fading," she said.