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When an adolescent is suspected of taking illicit drugs, parents, caregivers or schools may request that the adolescent complete a drug test. However, such testing of adolescents for non-evidential purposes is uncommon in general practice in New Zealand and it is unclear whether drug testing reduces substance misuse. Standardised interviewing techniques, e.g. HEEADSSS, are the first-line recommendation for detecting substance misuse in adolescents, as this provides contextual information about an adolescent’s behaviour. If drug testing is performed, adolescents need to understand their right to confidentiality, and support and assistance should be provided in the event of a positive result. N.B. The following article focuses on non-evidential drug testing.

The benefits of drug testing are unknown

Drug testing of adolescents is highly controversial and there is no evidence that it provides a clinical benefit in a community setting. However, if an adolescent, or their parents or caregivers, wish for a drug test to be performed, it is important that health professionals can explain the benefits versus the limitations of testing and, if necessary, be aware of the correct sample collection procedures.

The cost of drug testing

Drug testing that is requested by a General Practitioner for clinical reasons is funded (through usual laboratory contracts), e.g. to confirm/exclude drug use when treating a patient who may have over-dosed. Drug testing for non-clinical purposes, e.g. pre-employment screening or to assist an adolescent in returning to school following suspension, is not funded and will cost the patient, or their employer/school, approximately $60–70 for a standard screen. If the test is for evidential purposes or the results are disputed, a positive result will require confirmatory testing, at a cost of approximately $90 for each drug that is tested for.

The two sides of the debate

Advocates of drug testing claim that testing is a justifiable way to identify adolescents who might benefit from counselling and treatment. It is suggested that testing deters the initiation of drug misuse and encourages cessation as the consequences of detection outweigh the benefits of intoxication.1

Conversely, it is argued that many adolescents do not respond to deterrence strategies and that testing is a punitive practice which may also encourage adolescents to use substances that cannot be tested for.1 In addition, adolescents who wish to avoid testing may disengage from health services that insist upon it.

When might drug testing be appropriate?

Establishing and maintaining a strong relationship with an adolescent in primary care is important. There is a risk that promotion of drug testing by the clinician may undermine this relationship. In addition, there is no evidence to recommend drug testing as an effective strategy for reducing adolescent substance misuse. When drug use in an adolescent is suspected, psychosocial assessments are the first-line investigative tool as these provide contextual information about the adolescent’s behaviour. However, in some cases, adolescents may ask for a test to be conducted following instruction by a school Board of Trustees or due to parental or caregiver concerns.

Drug testing is also used as a tool for measuring compliance in specialist intensive treatment programmes, for people addicted to substances such as cocaine or opiates.2 However, a primary care practice would rarely be involved in collecting samples for drug testing for this purpose.

Consent and competency to consent

The issue of adolescent consent and competency in regards to drug testing is contentious. This is particularly difficult when there is external pressure from family or the school for the test to be conducted. Drug testing should always be discussed with the adolescent first, and their consent gained if aged 16 years or over. Consent is also required from adolescents aged under 16 years if in the judgement of the clinician they are considered to be competent (otherwise parental/caregiver consent is necessary).

In order to assess competence, the clinician must form an opinion of the intellectual maturity of the adolescent and also be aware of the adolescent’s rights that accompany this assessment. This is referred to as the principle of Gillick competency, where children who are aged under 16 years, and have sufficient intelligence and comprehension, can consent to a treatment without the need for parental approval (i.e. they are Gillick competent). The adolescent should understand the nature, purpose and possible consequences of the drug test.

Issues surrounding confidentiality of test results also need to be considered and agreed upon. All adolescents should be strongly encouraged to discuss any drug test results with their parents or caregivers. However, if the adolescent is aged over 16 years or is “Gillick competent” for the purposes of drug testing, then the results of the test must remain confidential, unless the adolescent chooses to disclose the information to their parent or caregiver.

Limitations of testing

The limitations of drug testing should be explained to the adolescent and their parents or caregivers before any testing is performed. The principal limitation is the lack of contextual information that is gained by drug testing alone. In order to support adolescents who may be misusing drugs, it is important to know the frequency of drug use and to understand the social and developmental factors that may be causing the behaviour. A psychosocial welfare assessment is likely to be of greater clinical value to the adolescent and to place less strain on the patient-practitioner relationship (see “Assessing potential substance use with HEEADSSS, SACS and CRAFFT”).

Substances can generally only be detected if taken less than 72 hours before sampling, however, cannabis (tetrahydrocannabinol) can be detected from three days to three months later, depending on frequency of use (Table 1).3,4 Therefore, a positive test result for cannabis does not necessarily indicate that it is currently being used.

A positive test will not provide any information on the amount of drug that has been taken or the levels of impairment that it has induced. Furthermore, for some drug classes, a positive test does not always confirm that the drug use has been illicit. Depending on the testing and analysis method, positive results for opiates can be produced by any medicine that contains codeine, by fluoroquinolones, or by eating foods containing poppy seeds, e.g. one poppy seed muffin or two poppy seed bagels (N.B. this may occur in a preliminary drug screen, but would be very unlikely to occur with confirmatory testing).5 The antidepressant sertraline can also produce a positive test for benzodiazepine use.5

A negative test will only confirm that the drugs that have been tested for are below detection limits. Inhalants are a relatively common substance of misuse, but are unable to be detected by drug testing. Some drugs such as oxycodone, methylphenidate (Ritalin) and ecstasy are not detected by standard screens. Testing for these substances must be specifically requested.

Assessing potential substance use with HEEADSSS, SACS and CRAFFT

New Zealand guidelines recommend that every adolescent’s psychosocial welfare be routinely assessed. HEEADSSS (Home, Education, Eating, Activities, Drugs, Sexuality, Suicide, Safety) is a standardised tool, intended to be used as a guide to a psychosocial assessment.7 Questions are formulated and asked by the clinician, based on the topics within the HEEADSSS acronym. A psychosocial assessment should be conducted on all adolescents suspected of substance misuse regardless of whether or not drug testing occurs.

For further information about performing a HEEADSSS assessment, see “Substance misuse in adolescents” BPJ 42 (Feb, 2012).

If an adolescent discloses drug use during an assessment, this should be investigated further with tools such as the Substances and Choices Scale (SACS) or CRAFFT. SACS is a detailed question set, developed and validated in the New Zealand population. CRAFFT is a simple, but less informative, method for assessing the degree of risk that drug taking may expose an adolescent to.

N.B. Both HEEADSSS and SACS can be accessed within the bestpractice decision support module “Depression in Young People”.

For more information about SACS and a copy of the questionnaire see:


  1. Have you ever been in a Car driven by someone (including yourself) who had been using drugs?
  2. Do you ever use drugs to Relax, feel better or “fit in”?
  3. Do you ever use drugs when you are Alone?
  4. Do you ever Forget things you did while using drugs?
  5. Have Family or friends ever told you to “cut down” your use of drugs?
  6. Have you ever got into Trouble while you were using drugs?

Answering “yes” to two or more questions indicates that drug use is likely to be a problem. Particular “red flags” are drug use when the adolescent is alone and friends expressing concern about usage.

Table 1: Length of time drugs can be detected in urine samples (adapted from Standridge, 2010)6

Drug class Detection window
Amphetamines Two to three days
Benzodiazepines Three days for short-acting (e.g. lorazepam), up to 30 days for long-acting (e.g. diazepam)
Cocaine Two to three days, but up to eight days with heavy use
Opiates One to three days
Tetrahydrocannabinol Three days with single use, five to seven with use at four times per week, ten to 15 days with daily use and up to three months following heavy, chronic use

Performing a non-evidential drug test

Drug testing can be carried out for evidential or non-evidential purposes. Evidential testing is required for certification, legal or other evidential reasons such as pre-employment, post-incident, visa applications and drug rehabilitation programmes. As these tests may have evidential or legal implications, specimens need to be collected and tested in accordance with standardised procedures at accredited laboratories. Positive preliminary tests are followed up by confirmatory testing.

Drug testing at home is not recommended

Although drug testing kits can be readily purchased online, the American Academy of Pediatrics has expressed strong reservations about drug testing of adolescents in the home setting.3 Information on how to “pass” (falsify) drug tests is freely available on the internet, along with products such as synthetic urine (including heating devices). In a home setting it is difficult to replicate the conditions required to ensure that urine samples are not contaminated or substituted. Home-testing is also likely to place strain on family relationships.

Drug testing adolescents in the general practice setting, for the purposes of counselling and compliance is non-evidential testing. Non-evidential testing is still performed under a robust process, but does not require a sample to be collected under the observation of certified personnel, or for the sample to be subject to “chain of custody” protocols when it is transported and stored. Confirmatory testing is also not necessary, unless the test result is disputed.

If the adolescent wishes to proceed with the drug test, after considering the limitations of drug testing and discussing more preferable methods of psychosocial assessment, the following protocols should be observed.

Specimen collection

Urinalysis is the preferred method for drug testing in general practice. Analysis of saliva and hair samples may be available via ESR or private laboratories. It is also possible for blood, breath and sweat to be analysed. Urine generally contains higher drug concentrations than blood, breath or hair.8 Drugs and/or their metabolites are also usually present for longer periods in urine than in blood.9

Before taking a sample for analysis, a detailed history of all medicines the patient is taking, or has recently taken, should be noted; including all over-the-counter (OTC) and herbal preparations. This list should be recorded on the standard laboratory request form. It is important to record any specific substances that the adolescent is suspected of taking. This is because the standard preliminary screen may not detect some drugs and specific testing may be required.

Urine collection protocol

Although “chain of custody” protocol is not required for non-evidential testing, it is important that urine is collected following set protocols. A robust collection protocol removes any suspicion that the sample may have been deliberately contaminated, diluted or substituted during the collection procedure.

The adolescent should remove outer clothing (e.g. jacket) that might conceal anything that could contaminate or dilute the sample, and then wash and dry their hands. The chances of a sample being deliberately contaminated are reduced if the collection procedure takes place in a cubicle where the toilet contains a bluing agent and there are no other sources of water present. Direct observation of urination is not compulsory for non-evidential drug testing, however, this is likely to provide a strong deterrent to contamination of the sample. A 2007 report on random drug testing in an adolescent substance misuse programme suggested that contamination of samples by adolescents may exceed 20% in uncontrolled situations such as a general practice clinic.11 Anecdotal reports suggest that the actual number of deliberately contaminated samples is likely to be much higher.

A sample volume of at least 30 mL is recommended (although smaller volumes may still be adequate).10 Once a sample has been provided the patient’s name, NHI number and the date and time of collection should be written on the container which the adolescent should also initial. The accompanying testing form should be clearly labelled to ensure all data matches.

How to tell if a sample has been contaminated

An unusually hot or cold sample, a very small volume, or unusual colouration are all indicators that the sample may have been interfered with. Creatinine concentration is reported with urinalysis results as a way of confirming sample authenticity. Normally, urine has a creatinine concentration > 1.75 mmol/L. A specimen with a low creatinine concentration (especially below 0.5 mmol/L) is most likely to be diluted or otherwise adulterated.

Primary screening and secondary confirmation

Most laboratories perform an immunoassay on urine samples. A standard preliminary drug screen covers compounds in the following classes:

  • Amphetamines
  • Benzodiazepines
  • Cannabinoids
  • Cocaine
  • Opiates

If an adolescent has taken drugs illicitly then a positive preliminary screen is often sufficient for them to acknowledge the behaviour. Secondary confirmation is usually offered by the laboratory, but in non-evidential testing it would only be required if the test result is disputed. N.B. confirmatory testing is mandatory in evidential drug testing.

Confirmatory testing involves the use of gas chromatography and mass spectrometry. Laboratories who are not equipped to offer this service can refer samples to the limited number of laboratories in New Zealand who do this testing.

Interpretation of results

A positive drug test does not always mean that the drug use has been illicit. One study which analysed 710 drug tests performed on people aged 13 – 21 years, found that 21% of positive drug tests resulted from the use of legally prescribed or purchased OTC medications, including 91% of samples positive for amphetamines.11 False-negative results are also possible – the same study also found that 6% of samples were reported as negative because they were too dilute to interpret.11

Managing a positive result

Following a positive result, it is crucial to understand how much risk the adolescent is exposed to, what is driving any drug taking behaviour and the social context that the drug taking is occurring in. A discussion guided by HEEADSSS and SACS is the best tool for General Practitioners to uncover this information.

There is a danger that a positive drug test may cause an adolescent to become stigmatised, resulting in a reduction in self esteem and exacerbation of any underlying mental health conditions or negative social influences and disengagement from health services.1 Referral for further support, and where appropriate, psychosocial interventions should be offered. Self management, brief interventions, motivational interviewing and cognitive behavioural therapy can all be used to assist adolescents who are at risk due to substance misuse.

It has been estimated that 60 – 75% of adolescents with a substance misuse disorder have some form of mental illness.12 Therefore it is important that any underlying medical disorders are identified and effectively managed. Adolescents who display symptoms of suicidality, self-neglect, psychosis, severe depression or suspected bipolar disorder should be referred urgently to secondary care mental services.

Informing parents/caregivers

Adolescents who return a positive drug test should be strongly encouraged to discuss this result with their parents or caregivers. Ideally, this discussion will involve the General Practitioner. Test results may only be disclosed to parents or caregivers with the consent of the adolescent (unless judged not to be competent). However, in cases where the adolescent is believed to be placing themselves or others at risk through substance misuse, the clinician may disclose information to a parent or caregiver without the adolescent’s permission. In such cases a Child, Youth and Family Services (CYF) referral should be considered. If a school or employer contacts a practice concerning an adolescent’s test results, this information should remain confidential, unless there is prior consent for the information to be released.

For further information see: “Substance misuse in adolescents: alcohol, cannabis and other drugs”, BPJ 42 (Feb, 2012).

LabPLUS is an Auckland based laboratory that provides both evidential and school-based non-evidential drug testing. For further information see:

ACKNOWLEDGEMENT: Thank you to Patricia Mitchell, Maria Kekus and Mo Harte, Connect4Health, Nurse-led Youth Health Service, Auckland for expert guidance in developing this article.


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