Alzheimer's could potentially be diagnosed using a simple blood test in the future, following a discovery by scientists in Spain.

Led by Pedro Carmona from the Instituto de Estructura de la Materia in Madrid, the research team developed a non-invasive, fast and low-cost way to not only diagnose Alzheimer's, but also detect which stage the disease is at.

According to the team, the test offers accurate diagnosis of both mild and moderate stages of the disease.

It does this by measuring how much infrared light is either emitted or absorbed by white blood cells. Current tests for the disease are invasive and seek to determine levels of amyloid-ß peptide in the cerebrospinal fluid.

Alzheimer's patients are also thought to carry amyloid-ß peptide in their blood, and it is this which the researchers hope to exploit with their new test.

They recruited 50 patients with Alzheimer's disease and 20 patients without the disease for a control group.

Two-dimensional infrared spectroscopy was then employed to compared the radiation emitted or absorbed by white blood cells in patients with mild, moderate and advanced Alzheimer's and the control group.

The resulting difference in the infrared wavelengths witnessed between patients was thought to be due to the different stages of formation of amyloid-ß structures in the blood cells.

Subjects who were healthy could therefore be distinguished from those with mild and moderate Alzheimer's based on their results.

The authors of the study, published in Analytical & Bioanalytical Chemistry, said: "The method we used can potentially offer a more simple detection of alternative biomarkers of Alzheimer's disease.

"Our measurements seem to be more sensitive for earlier stages of Alzheimer's disease, namely mild and moderate."

Recent research suggested Alzheimer's biomarkers could be detected in the cerebrospinal fluid up to five to ten years before the symptoms of the disease become apparent.

The team found levels of Aβ42 are decreased long before those with mild cognitive impairment (MCI) develop Alzheimer's. They also suggested other fluids could act as biomarkers are the disease progresses to the later stages.