As an ultrafiltrate of the blood, saliva or oral fluid could present as a suitable medium to verify the presence of drugs of abuse. And not only that: in contrast to urine, saliva could also provide information regarding the level of current intoxication, which would be of great significance for roadside testing. No one would have to urinate into a cup or expose their genitals.
However, there is a whole series of problems and unanswered questions with regard to saliva, which must be taken into consideration:
- It must be assumed that the saliva is subject to significant variations from one subject to another. Saliva secretion is a complex process, and anatomical/histological conditions play an important role. Even factors such as stress, hunger or underlying systemic diseases may have an influence on the composition and consistency of saliva. As a result, standardisation of the method is practically impossible.
- Different substances reach the oral fluid through different ways and in different forms. For example, cannabinoids can be detected only for 30 minutes after onetime use. The detection time for ocaine and its metabolites is significantly longer. However, their detection time is dramatically affected by chewing gum or lemon drops (Halwachs 2011). At the least, the latter clearly challenges the theory that saliva cannot be manipulated. However, further investigation is certainly required.
- The volume of saliva collected in any one sample is very small. Therefore, saliva production is simulated – often by the saliva collection systems themselve by using acidic media. This influences the pH-value of the sample and thus influences the substances searched and their detection times. In addition, stabilizers are used for transporting the sample. These as well can influence the analysis. Nevertheless, further research in this regard is urgently required.
- The simulation of salivary flow itself represents in intervention in bodily functions, making such procedures impermissible for example in penal institutions. For more information please refer to our section In Penal System/Probation Services.
- The low sample volume requires highly sensitive and expensive analytical methods. There are quick tests available in the market. But major international studies such as ROSITA or DRUID do not recommend these tests due to high probability of errors and lack of standards with regard to threshold values.
It can be summarised that the saliva as a medium has a huge potential, but it has not been researched adequately to use it in clinical practice. You can find more information about this topic in our Download Centre.
Any mixture of tissue fluid and blood is defined as capillary blood, which is collected by piercing fingertips or ear lobes.
Blood as a medium has been researched adequately. However, capillary blood is not pure blood, which results in certain problems:
- Differences in the analysis of capillary blood and venous serum or whole blood are well documented. Thus, blood sugar measurement from capillary blood is no longer permitted for diagnostics, therapy and post-operative care of gestational diabetes since 2011. Even deviations in the blood gas analysis were established in many studies. Therefore, capillary blood is not recommended.
- Capillary blood contains a natural trace of tissue fluids. In order to minimise this, the first few drops should be rejected. However, it is hardly possible to quantify the proportion of tissue fluids.
- This problem is exacerbated by the stimulation of insertion point. This can be done only with suitable hyperemising ointment or heating, because mechanical simulation like massage or pressing will further change the composition of the collected sample.
- In addition, there is the risk of contamination, because taking samples with capillary tube is not a closed system. The research regarding possible contamination – e.g. due to hyperemising ointments – and its influence on tested substances is surprisingly sparse.
- The extremely low quantity of sample drastically limits the reproducibility of the analysis. As a result, it significantly increases the probability of errors.
- It should be noted that even this method of collecting capillary blood represents bodily intervention. Thus, the same legal consequences for saliva are applicable here as well.
It can be summarised that the capillary blood as an alternative for urine in clinical practice has not been researched sufficiently. Various medical fields show that ointments, for example, may have an influence on the analysis. Whether and to what extent it can influence the substance abuse requires more research. However, capillary blood is not above suspicion of providing protection against manipulation attempts.
Uncertainties regarding the above questions appear to be substantiated in scientific research:
Böttcher, Rönitz and Dahmen submitted the results of a study in 2014, whereby the objective of the study was to check whole blood as an alternative medium for EtG determination. They reached the conclusion that whole blood represents a possible alternative to urine for EtG evidence and thus “perhaps may be collected in future even as capillary blood”.