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Unexpected results

Occasionally results from tests carried out using Concateno's point of care oral fluids and urine testing products may be unexpected or disputed by the donor.

For example, a donor may claim to have used drugs but then test negative, or may disagree with a positive result. There are several reasons why you may get a test result that you or the donor did not expect.

Unexpected results can, in some cases, be due to procedural or operational errors made when carrying out the test using a point of care (on-site) test kit. Point of care test kits come with a set of user instructions that should be followed closely, and it is also recommended that, where appropriate, training in how to use the kits is provided. To optimise accuracy when testing it is important that the following points are strictly adhered to.

 

For an oral fluid sample, the client should not have had anything to eat, drink or smoke for at least 10 minutes prior to the sample being collected (this includes chewing gum and sweets).

  1. Check that the product that you are using is within the expiry date
  2. For dip and read products, ensure that you have not exceeded the immersion line
  3. Ensure that the test results were read within the timeframe stipulated in the test instructions/package insert. Test results can take a few minutes to develop and may fade over time
  4. The silica gel packs in the foil pouches should be yellow/orange not green
  1. The cartridge must be kept flat during sample application and insertion into the Cozart® DDS instrument.
  2. Sample should be added to the small sample well only.
  3. Add 4 drops to the test cartridge. Drops should be of even size and applied to the cartridge via the small sample well only. If the sample does not appear on the large test window after 30 seconds a 5th drop may be applied to the small sample well. Discard the cartridge if the sample fails to run after 5 drops are added.
  4. SYS and SQC tests should be performed on the Cozart DDS® on a regular basis to ensure that your instrument is performing accurately. Instructions for changing the test selection for performing these maintenance checks can be found on the Cozart DDS® Training Instruction Manual.
  5. Ensure that the Cozart DDS® instrument is set to read the correct drug selection. The drug test selection displayed on the Cozart DDS® should match the type of test cartridge you are using, which is printed on the outside of the foil packaging and also on the test kit box.
  6. DO NOT repeat a Cozart DDS® test on a sample. If you are concerned as to the results of a test please retain the sample and contact Customer Services who will be happy to advise you and offer additional testing.

Point of care (or 'instant') tests only provide a guideline indication to drugs or drug groups detected in an oral fluids or a urine sample, often known as a 'screening test'. If court proceedings or legally defensible actions are required to be taken on the basis of the outcome of a drugs test, a laboratory based 'confirmation test' is strongly recommended. The table below summarises the common reasons for an unexpected result from a point of care (on-site) test

Obtaining a negative result, despite a donor claiming to have used drugs, can occur for the following reasons:
 

Obtaining a positive result which is then disputed by the donor, may occur for the following reasons:
 
Purity of substance used - This can vary greatly and cannot always be controlled by the user. The higher the purity of a drug, the longer it will remain detectable in the user’s system. Though a donor may claim to have recently used, a low purity sample may be undetectable sooner than expected.
 		 Medication - Use of prescribed or over the counter medication such as painkillers or cough syrups may give a positive result as some brands contain substances similar to those detected by the drug screen.
 
Method of use - How a substance was taken will influence its window of detection in the body.
 		 False claims - A donor may intentionally be misleading about their recent drug use, or can be confused or unsure of what, when and how much of a drug they have taken. For example, some drugs can be cut with other substances or drugs that are unknown to the user.
 
Regularity of use – An occasional drug user is likely to have a much shorter detection window than that of a regular user. The time between drug use and sample collection can be critical in the detection of drugs when a low dose is taken.
 		 Regularity of use – Regular users build up a drug tolerance and tend to take increasingly larger amounts of a drug. This can lead to an increased window of detection for some drugs which may result in a positive test despite the client having not used recently.
 
Metabolism of user – The rate at which a drug is broken down and excreted by the body will vary from person to person and is governed by the individual’s unique metabolic rate. Those with a fast metabolic rate may excrete drug
substances quicker than those with a slower metabolism. Ill health may affect the rate of metabolism of drugs, therefore altering their window of detection in the body.
 		 Procedural errors - Failure to follow the correct sample collection and testing procedure for a point of care (on-site) test may lead to inaccurate results. The instructions sent with test kits should be closely followed, and where appropriate, training should be provided in advance of using the kits.

 

  1. Concateno point of care tests provide a preliminary screening test result. It is advisable that all samples giving positive results should be further tested and confirmed by Mass Spectrometry which can be conducted in Concateno's analytical labatories.
  2. In general, drugs or their metabolites will be detectable (ie, above the cut-off level) in a urine sample for longer than in oral fluid sample.
  3. Detection windows are very variable from person to person. In addition, some factors that can affect the detection window are the amount or purity of drug used, and the ability of the individual to metabolise/eliminate the drug from their system.
  4. If test results are disputed, samples can be subjected to further testing and confirmation by laboratory methods. Do not be tempted to take a new sample or repeat a test in light of an unexpected result.
  5. The results from an oral fluid drug test cannot be compared with those of a urine test. These biological matrices may display different windows of detection and represent different routes of elimination of the drug.

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