How adulteration works

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Let’s talk about adulteration in drug testing (also known as cheating).

It’s a commonly used concept to refer to three different types:

  • substitution — using someone else’s urine, synthetic urine, or a different substance altogether.
  • dilution — diluting the urine sample so the levels of drugs present drop below the cut-off level. The dilution can be in vivo (drinking excessive amounts of water) or in vitro (adding water to the urine).
  • addition — adding substances to the urine sample to prevent the drugs from being detected.

The way to prevent substitution is through your drug testing procedures: check the person isn’t carrying any containers or bags of liquid, ask the person to pat themselves down and to take off any heavy jackets or clothing items that can hide containers, and make it difficult for a liquid to be transferred if a container is smuggled through.

To catch dilution, the urine sample needs to be analysed to see if it matches the characteristics of a normal urine sample. In addition, the environment should be prepared to make it impossible to dilute a sample: drop a blueing tablet in the toilet cistern to prevent water being scooped into the cup, tape up any taps inside the room, tape windows closed to prevent water being passed in from outside.

To catch addition, the process is similar for dilution. The urine sample needs to be inspected and analysed to see if it matches the characteristics of a normal urine, and your drug testing procedures need to make adulteration difficult to achieve. Get the person to wash their hands before testing to remove any substance on their hands/under their fingernails, and stay alert for any signs adulteration is being use

Urine testing cups have an adulteration panel. They will test for a combination of the following adulterant indicators (a good cup will have most or all):

  1. Creatinine (required by the AS/NZS 4308 standard)
  2. pH
  3. Oxidants (may be named Bleach)
  4. Nitrites
  5. Specific Gravity
  6. Glutaraldehyde
  7. Pyridinium Chlorochromate

Stay tuned to our email newsletter, we will cover the meaning of each adulterant indicator, what substances are used to cheat, and procedures for detecting and preventing substitution and dilution.

Alcohol testing measurements

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Different countries around the world use different measures of alcohol in breath.

In New Zealand, we use micrograms of alcohol per litre of breath: in a given litre of breath, how many micrograms (one millionth of a gram) of alcohol does the breath contain?

The symbol for this is μg/L. The current drink drive limit is 250 μg/L, and the DIC (criminal) limit is 400 μg/L.

Most company policies state cut-offs of 0 μg/L or 100 μg/L, with 0 μg/L being the most common.

New Zealand is fairly unusual, using μg/L. The only other countries around the world that use this are Botswana and the Netherlands!

The alternative that we see most often is grams of alcohol per two hundred and ten litres of breath: in two hundred and ten litres of breath, how many grams of alcohol does the breath contain? This is commonly used in Australia and America.

The abbreviation for this is g/210L. In this measurement, our current drink drive limit is 0.052 g/210L, and the DIC limit is 0.083 g/210L.

The updated standard for breathalysers, AS 3547:2019, specifies that breathalysers should measure in g/210L. This is a real pain for New Zealand – we have built up intuition over years of testing that 20 μg/L is a low result and 500 μg/L is a high result. That intuition suddenly no longer applies when being faced with readings like 0.0042 g/210L and 0.105 g/210L!

It remains to be seen how New Zealand will respond to this standard: whether we adopt it entirely and switch measurement units, or whether we adopt it in part and keep using μg/L.

If our measurement ends up changing, the magic number to convert between measurements and get an approximate result is 4,762. To get from μg/L to g/210L, divide by 4,762:

250 μg/L ÷ 4,762 = 0.052 g/210L.

To get from g/210L to μg/L, multiply by 4,762:

0.08 g/210L × 4,762 = 380 μg/L.

Drug testing devices need to be room temperature

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Drug testing relies on reactions between antibodies (on the test strip) and antigens (in the sample, the substance being tested for).

At a lower temperature, reactions occur slower, or not at all.

If your cups are cold you will get inconsistent results, often: panels failing to run, weak/patchy lines, or colours failing to appear on the temperature strip.

Make sure your cups are warm before testing!

For storage, store your cups in a warm office or cupboard, at the temperature range the manufacturer suggests. This is usually from 2°C – 30°C.

When using a cup, the temperature range is smaller. Follow the manufacturer recommendations, usually this is from 15°C – 30°C.

Cold warehouses and vehicles can present a challenge in winter to keep cups at an ideal temperature, but a bit of planning can eliminate these concerns. Have enough cups stored in the office for a few days of testing (plus a some extras for those last minute requests!).

Cups should be stored in an insulated room overnight, as the minimum — a couple of hours in a warm office is not going to be enough to warm up really cold cups, as they’re fairly well insulated in their foil wraps.

Whoops – I ran a test and suspect the the cup was too cold. What can I do?

If you think you have an abnormal result you can test again.

If you’re using a split cup (like the Medix Pro-Split cup), the portion of the sample being tested is split off from the rest of the sample. You can pour the rest of the sample into a new, warmer cup, and repeat the test.

If you’re using a screw top cup (like the MicroScreen cup), ask the donor to give another sample.

As always, these cups are a screening test only. If in doubt after testing again, send the sample to a laboratory for confirmation.

How drug tests work: the technology

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Drug testing seems simple – you just run the test and read the result. However, behind this simplicity hides a lot of complexity.

Drug tests use competitive lateral flow immunoassay technology. Here’s what the italicised words mean, broken down:

Competitive format: this means that two lines = negative, one line = not-negative. This is the opposite of a sandwich format test, where two lines is positive (the most common example of this is a pregnancy test).

Lateral flow: the urine or saliva starts at one end of the strip, and flows laterally (along) the strip.

Immunoassay: a test for the presence of a molecule, using antibody/antigen reactions.

This is a complicated and interesting technology, which enables quick point-of-care testing.