Analytical tests for the determination of cannabis use (clinical analyzes)



Natural cannabinoids or phyto-cannabinoids are chemical substances (so far 65 have been identified) naturally occurring in the plant Cannabis Sativa. Cannabinoids act on the central nervous system, for example on the brain, triggering effects capable of modifying the psycho-physical state of a person such as, for example, perception, mood, consciousness, behavior (psychotropic effects).

The most studied cannabinoid, also for its undesirable effects (side effects) on the body, is tetrahydrocannabinol (THC). Many of the cannabinoids present in the Cannabis Sativa they have not yet been studied; other cannabinoids, on the other hand, are completely unknown.

At the Cannabis Sativa the cannabis plant belongs, from whose dried female inflorescences marijuana is obtained. Marijuana contains several cannabinoids, the main one being delta-9-tetrahydrocannabinol (Δ9-THC), with which psychotropic effects are mainly associated.

The use of cannabis is currently permitted for medical purposes only for certain diseases.

The analysis for the research of cannabinoids in the organism is carried out on urine, blood, saliva and hair and is generally requested for clinical and / or medico-legal purposes such as:

  • identification of the causes of acute or chronic intoxication
  • psycho-physical fitness to drive
  • suitability for particular insolvency rules
  • determination of drug addiction
  • suitability for custody of children, in cases of marital separation
  • absence of prohibited anti-doping substances

In the event that the assessments are necessary as judicial evidence, and therefore with a medico-legal value, they must have precise requirements of certainty and reliability.

More rarely, analytical tests of cannabinoids may be required to verify the efficacy of the extracts of the Cannabis Sativa for medical use in the following cases:

  • chronic pain, multiple sclerosis, spinal cord injuries
  • side effects of chemotherapy and radiotherapy, in cancer patients
  • side effects of retroviral therapies, in people who have tested positive for human immunodeficiency virus (HIV)
  • eating disordersassociated with oncological diseases or acquired immunodeficiency syndrome (AIDS)
  • reduction of involuntary movements, in Tourette's syndrome

Analysis for the research of cannabinoids in biological matrices

To obtain information on the consumption of cannabis, the analysis for the search for cannabinoids is performed on the urine. The advantages are: non-invasive sampling, possibility of testing large volumes and analyzing the parent substance and / or its metabolites after several days.

In case you want to establish a topicality of use, the analytical assessment is performed on the blood (invasive sampling) or, alternatively, on the saliva (a sample of saliva is collected through a swab carried out on the gum or on the internal wall of the mouth).In the event that the detection window needs to be increased to evaluate an older cannabis use, the analyzes are performed on the hair taken from the back of the head as close as possible to the scalp.

Umbilical cord blood and / or meconium (newborn stools evacuated within 24 hours of birth) are analyzed to assess fetal exposure to substances of abuse used by the mother during pregnancy.

Before carrying out the analyzes, first of all, it is necessary to report to the healthcare professional all the information about any medications you are taking, including those containing cannabis. If the test is performed on saliva, it will be necessary not to have eaten or drunk in the 10 minutes before sampling in order not to alter the response of the analyzes.


Initially, screening tests are performed that exclusively produce a qualitative result, namely probable positivity (better defined as "non-negativity"), i.e. the presence in the biological matrix examined of a quantity of cannabinoids above a threshold value (" cut-off "), different depending on the matrix on which the test is performed (urine, blood, saliva, etc.). If the result obtained with the screening test is positive, this must be confirmed using a specific method for the type of substance analyzed Generally, the confirmatory test consists of a technique called di chromatographic separation coupled to the mass spectrometry. Also in this case the threshold values ​​are different depending on the biological matrix analyzed. Remember that any value obtained must be viewed and interpreted by a specific professional figure such as the toxicologist.

A positivity to a confirmatory analysis does not provide any information about how the substance was taken and cannot distinguish whether the use of cannabis was for health or recreational reasons.

As regards the determination of delta-9-tetrahydrocannabinol (THC), there are medical devices on the market, including in pharmacies, the result of which must be interpreted based on the presence / absence of colored bands after wetting the strips of the medical device in the urine sample. A negative result does not necessarily mean that the person being tested is not using cannabis. In fact, THC may be present at such concentrations that it cannot be detected or has already been eliminated by the body. Furthermore, the period of time during which THC is detectable, after taking cannabis, varies from person to person. since it is influenced by the individual metabolism, the dose taken and the frequency of use. The analyzes may be able to detect cannabis intake from 3 days up to 30 days before their execution. Regular cannabis users can test positive even for periods longer than 30 days from the last intake.

Some studies have shown that positive THC results can also occur in people who have not smoked cannabis due to secondhand smoke.

As for synthetic cannabinoids, they represent a vast family of molecules structurally unrelated to each other but functionally similar to Δ-9-tetrahydrocannabinol (THC), produced in chemical-pharmaceutical laboratories and considered alternative forms to simple marijuana. Synthetic cannabinoids bind to the same CB1 and CB2 receptors as THC in the brain and other organs but with different effects.These substances can have unpredictable and potentially life-threatening effects, including the onset of seizures, brain edema, heart problems and psychosis. The analyzes used for the determination of THC do not allow to detect the presence of synthetic cannabinoids in the various matrices and therefore specific analytical determinations are necessary.


Pichini S, Pacifici R. Guidelines for the determination of substances of abuse in the urine

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