SALIVA DIAGNOSTICS
with a fear of needles, and anxiety during sample collection can potentially influence cortisol levels, ultimately affecting the test results. From a safety perspective too, the low concentrations of HIV and hepatitis antigens in saliva mean that the risk of infection to third parties is much lower than when handling blood samples.
Saliva testing overcomes these challenges, as it is safe, non-invasive, easily repeatable and can be performed in any setting, enabling patients to collect regular samples in the comfort of their own homes without requiring medical supervision. Most analytes in saliva are also stable at ambient temperatures for up to a week, allowing samples to be collected and shipped without refrigeration.4
However, even though Immunoassays like the Tecan Cortisol Saliva ELISA allow the quantification of free hormone levels in saliva.
presents an issue when using serum samples to test for hormone levels, since 95-99% of hormones present in the blood are bound to carrier proteins – or conjugated – leaving them metabolically inactive and unable to act on a target receptor or tissue. Current serological tests are unable to distinguish between conjugated and unbound hormones, so analysis of blood samples leads to an artificially high reflection of the active hormone levels in the body. Blood tests are invasive, making it challenging or even unethical to collect samples repeatedly from some patients due to cultural reasons, age, or physical or mental disabilities, and they also require trained professionals to perform the blood draw, limiting the times and locations that hormone monitoring can take place. Fortunately, the analysis of saliva samples can provide more accurate results without any of these limitations.
Saliva sampling
Saliva contains many of the same hormones that are found in blood, and
their relative concentrations fluctuate in tandem. However, saliva only contains unbound hormones, since conjugated molecules are too large to diffuse through the salivary gland membrane. Consequently, saliva testing is capable of accurately determining the levels of biologically active hormones available to target tissues.
The benefits of saliva testing do not end with accuracy though; there are several other advantages over blood and urine analyses for clinicians and patients alike, particularly in terms of convenience. For instance, while 24-hour urine collection is a valid method for hormone monitoring, it can be inconvenient for patients, and only measures the total amount of a hormone produced without offering insights into its fluctuation over that period of time. Similarly, studying diurnal variations in cortisol requires multiple blood samples to be taken throughout the day, but repeated sampling can be impractical due to the invasive nature of blood drawing. It can also be a stressful process for patients
As well as accuracy, saliva testing offers several other advantages over blood and urine analyses for clinicians and patients alike, particularly in terms of convenience
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saliva is less likely to deteriorate than blood prior to testing, the validity of any results will largely depend on the initial quality of the collected sample, which makes it important to consider the following points: n Sampling strategy: the concentration of many analytes in saliva can vary significantly depending on the time of day or month, so a clear sampling strategy must be decided upon to ensure that collection takes place at suitable intervals.
n Fasting: it is recommended that an individual should fast for a minimum of 30 minutes – as well as rinse their mouth out with water – before the collection of saliva samples.
n Saliva collection: to guarantee convenient and consistent sample collection, the passive drool method is recommended – allowing saliva to flow to the base of the mouth before drooling into the collection tube.
n Volumes for analysis: the sample volume will depend on the number of analytes of interest. The more hormones that need to be quantified from a single sample, the larger the volume of saliva that must be collected.
n Blood contamination: samples with even the slightest red tint should be discarded – since the total steroid concentration in blood can be up to 100 times higher than in saliva – to avoid compromising result integrity.
n Drugs and medication: some prescription drugs can significantly influence hormone concentrations, so it is important to know what medication the patient is taking.
Hormone analysis
The demonstratable benefits of using saliva to diagnose hormone imbalances have led to the development of an
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