When in 2005 our research group managed to measure for the first time the C-reactive protein in saliva, one of the main markers of inflammation, it was difficult to imagine that tests in saliva could have such widespread and interest as they have recently achieved.
Without a doubt, the possibility of diagnose and monitor covid-19 in this fluid, made up of at least 95% water, but also other elements of high interest, has been a great impetus for people to talk about its possibilities as a biological sample in this disease. However, it is okay to remember that saliva has many more uses.
Detection of covid-19, but also of other infectious diseases
To begin with, in saliva a multitude of infectious agents can be identified, either by direct identification of their genetic material through PCR tests or by the quantification of specific antibodies that our body produces against it.
This has allowed some countries, including the United Kingdom, to establish official programs to detect infectious diseases such as rubella taking saliva samples with high sensitivities and specificities.
The thing does not end there. In addition to determining the production of antibodies (markers of the humoral immune response) in saliva, markers of the innate immune response can be detected. We refer specifically to the acute phase proteins e interleukins, but also to markers of the cellular immune response such as enzima adenosine deaminasa.
In short, from saliva you can obtain very valuable information about how our defenses are working at any given time.
Saliva to assess stress … and happiness
Worldwide 30% of people suffer from stress. Saliva can help detect and evaluate it. Thus, this fluid makes it possible to estimate both very short-term stress –alpha-amylase or chromogranin A– and longer-term stress –cortisol–. A marked increase in these analytes It would indicate the need to take measures to try to reduce the stress that the individual is suffering.
Apart from stress, saliva allows you to assess your well-being. For this, the oxytocin levels, considered as the “hormone of happiness”.
To complete the possible applications, it turns out that saliva can be used to evaluate the oxidative state of the individual and also physiological changes in different situations such as physical effort. In addition, it is useful for detecting drugs or measuring analytes that were traditionally measured in the blood, such as urea and creatinine. Without forgetting that the study of saliva by means of “omics” techniques could soon lead to new tests and applications of this fluid.
Applications in the animal world
Whether in companion animals, farm animals, or even exotics, saliva can be used for the same purposes that have been indicated for humans. From a practical point of view it is very interesting because, in pets, the owner can take the sample and give it directly to his veterinarian. How many bad times for blood draws and visits to the clinic we save pets like this!
In farm animals, the fact that the staff themselves can take the samples allows to improve the control of the health and well-being of the animals. At present, there is a european project which is precisely responsible for assessing how to assess the level of well-being and stress of the animals through saliva.
Despite having been working with saliva samples for more than 20 years, and having in our laboratory the most sensitive and reliable methods to measure its main analytes, we can only say that we are at the beginning of the road. Surely in the coming years this exhibition will bring us more pleasant surprises.
That’s Tvarijonaviciute, Doctor in Veterinary Medicine, University of Murcia; José Joaquín Cerón, Responsable of the Interlab-UMU research group, University of Murcia; María Pía López Jornet, , University of Murcia, and Silvia Martínez Subiela, Doctor in Veterinary Medicine, University of Murcia