Laser-based saliva test to help diagnose diseases early

A novel laser-based technique can analyse human saliva and non-invasively diagnose immune system disorders even before the symptoms appear, increasing the chances of recovery, scientists say.

Disorders of the immune system lead to various diseases from allergy and type I diabetes to more dangerous autoimmune diseases, such as multiple sclerosis.

However, such diseases are diagnosed only when the symptoms are clearly demonstrated.

Researchers of St Petersburg Polytechnic University (SPbPU) in Russia developed a unique method of immune diseases diagnosing before the symptoms appear.

They proposed a laser-correlation spectroscopic technique (also called dynamic light scattering) for studying the immune response in body fluids, for example, in saliva.

"We offer a cheap and effective method of diagnosing the diseases without any indication. We need a laser, a receiver and a programme for data analysis," said Elina Nepomnyashchaya, from SPbPU.

"In the course of routine clinical examination, saliva can be tested so that the patient can learn more about the disease before the symptoms appear. This method will increase the chances of recovery," Nepomnyashchay said.

It is known that saliva contains the same immune proteins as blood. Moreover, it is much easier and cheaper in comparison with blood analysis.

The proposed method is to analyse the scattered light obtained by laser illumination of humans biological fluid (saliva or blood).

The laser beam is focused on the sample. The proteins in the liquid scatter the light, which is registered by the detector.

By analysing the change in the intensity of scattered light in time, it is possible to determine the size of the particles floating in the liquid, researchers said.

The particle size changes during the activation of immunity, the proteins are binding and become larger.

In addition, the size composition of biological fluids in different people can vary. It depends on the certain diseases in the organism.

Thus, it is possible to determine whether the human body reacts to infections properly and to diagnose the diseases.

With this method, it is also possible to test medical drugs not on a human, but on his biological fluids, paving the way for custom treatments to suit the individual.

Such studies of the dynamics of the activation of immune proteins using optical methods have not yet been carried out, thus the research remains to be done.

The current task is to create a detailed study of the reactions of donors with various pathologies.