New York, Mar 3 (IANS): A simple blood test could soon tell if a person with memory problems actually has Alzheimer's disease, says a study which reported an advance in the development of the test.

The researchers believe that such a blood test could replace invasive and expensive current brain imaging and spinal fluid tests to detect Alzheimer's disease.

"Finding a blood test that specifically identifies the presence of Alzheimer's pathology in the brain should greatly help researchers develop better treatments for the many who suffer from dementia," said Roderick Corriveau, Programme Director at the National Institutes of Health's National Institute of Neurological Disorders and Stroke (NINDS).

The blood test detects the abnormal accumulation of a form of tau protein known as phosphorylated-tau-181 (ptau181), which is a biomarker that suggests brain changes from Alzheimer's, according to the study published in the journal Nature Medicine.

Over the past 15 years, research advances in the development of biomarkers like tau protein have enabled investigators to more accurately diagnose Alzheimer's disease, select research participants, and measure response to investigational therapies.

Tau and other biomarkers can be detected with Positron-emission tomography (PET) scans of the brain and lab tests of spinal fluid.

However, PET imaging is expensive and involves radioactive agents, and spinal fluid tests require spinal taps, which are invasive, complex and time-consuming.

Simpler biomarker tests are still needed.

An international team of researchers led by Adam Boxer at the University of California, San Francisco, used the new test to measure the concentration of ptau181 in plasma, which is the liquid part of blood that carries the blood cells.

The samples were collected from more than 400 participants from the University of California, San Francisco Memory and Aging Centre.

Their analysis demonstrated that the ptau181 in plasma could differentiate healthy participants from those with Alzheimer's pathology, and differentiate those with Alzheimer's pathology from a group of rare neurodegenerative diseases known collectively as frontotemporal lobar degeneration (FTLD).

A different international team, this one led by Oskar Hansson at Lund University in Sweden reported similar findings.

Using the same plasma ptau181 test, these researchers were able to differentiate between Alzheimer's and other neurodegenerative diseases nearly as well as they could with a spinal fluid ptau181 test and a PET brain scan for tau protein.

In addition, they followed participants for several years and observed that high levels of plasma ptau181 among those who were cognitively normal or had mild cognitive impairment may be used to predict later development of Alzheimer's dementia.

These results were also published in the journal Nature Medicine.