Drug Testing Frequently Asked Questions

The following are some of the commonly asked questions and answers about drugs of abuse testing in the workplace.
What is the collection procedure?
Samples for testing must be collected using the correct chain of custody procedure to ensure that the results are from the identified person.  Chain of custody is a legal term that refers to the ability to trace a sample from the time of collection to the reporting of results.
A chain of custody form accompanies each sample and must be completed correctly by every person who handles the sample.
Collection procedure usually involves:
  • positive identification of donor e.g. driver’s licence with photograph or passport;
  • precautions taken to minimise sample adulteration such as removing excess clothing and personal belongings, thoroughly washing hands, adding coloured cleaning solution to the toilet bowl, removing cleaning solutions from the collection area and making the hot water outlet inoperable;
  • the filled urine sample being kept in sight of both the donor and collector until sealed;
  • the collector immediately measuring and recording the sample’s temperature;
  • the collector tests for creatinine to check that the sample is suitably concentrated for a urine drug screen;
  • labelling of the sample including name, date of birth, date and time of collection; 
  • the sample and chain of custody form being placed in a biohazard bag.
What sample is most appropriate?
Urine is the best sample for substance abuse testing.  It is non-invasive, easy to obtain, can be collected under supervision and contains drugs at concentrations, which are easily detectable. PathWest have also validated methods for the analysis of some drugs of abuse in oral fluid.
How can you tell that a sample has been contaminated, substituted or adulterated?
There are several checks to ensure that samples tested are free from contamination or adulteration.
When the sample is collected the temperature is taken within four minutes and should fall within an acceptable temperature range of 33o- 38oC.  If the temperature falls outside this range it is likely that the sample has been diluted or substituted.
The level of creatinine in the sample is also measured and must be above 1.8 mmol/L to indicate that the sample has not been diluted in any way.  Creatinine is produced in the body and naturally excreted in urine.  In addition, the sample is also tested for compounds that may have been added to the urine to produce a negative result.
What drugs should be tested?
The normal drugs of abuse screening includes alcohol, amphetamines, benzodiazepines, opiates, cannabinoids, and cocaine.
Other drugs such as methadone and buprenorphine can be tested, but usage of these drugs is infrequent or restricted to certain populations and routine testing is usually not warranted.
What are the common names for the drugs tested?
   Class       Common names​
Amphetamines  Speed, Ecstasy​
Benzodiazepines​ Valium, Serapax​
Opiates    Heroin, Opium, Morphine, Codeine​
Cannabinoids   Cannabis, Marijuana, Hashish​
Cocaine Cocaine, Coke
What are the cut-off threshold concentrations for the screening tests and confirmatory tests?
The Australian Standard AS4308 details appropriate cut-offs for both the screening and confirmatory tests.
Class Individual Drug​ Screening  Tests (µg/l)  Confirmatory Tests (µg/l)*​
Delta 9-THC COOH    
     *    µg/l = microgram per Litre
     **   as Delta 9-THC carboxylic acid
     ***  as benzoylecgonine
How long after use are drugs likely to be detected?
The length of time for which a drug will remain detectable in urine depends on the rate of drug excretion in the individual, the quantity and frequency of drug use and the sensitivity and cut-off levels of the testing procedure. The table below gives some average detection times for common drugs of abuse.
Drug     Approximate Detection Time​
Amphetamines     2 days​
Benzodiazepines​ 3 days if therapeutic dose ingested
Up to 4-6 weeks after chronic dosing     
Cannabinoids    Moderate smoker (4 x week)                       5 days
Heavy smoker (daily)                                    10 days
Chronic smoker (daily for months)            20 days or more
​ Cocaine    2-4 days​
Ethanol      2-14 hours​
Methadone​ 3 days​
Opiates      2 days​
What contributes a presumptive positive result on the screening test?
A presumptive positive result occurs when the sample contains drug at or above the recommended cut-off threshold.  Samples that contain no drug or drug at concentrations below this threshold are reported as negative. All presumptive positive results must be confirmed by a different analytical technique such as GCMS.
What method is used in the confirmation test?
Mass spectrometry (MS) is the only method recommended by the Australian Standard for drugs of abuse testing in the workplace. PathWest operates two Mass Spectrometry techniques: Gas Chromatography Mass Spectrometry (GCMS) and Liquid Chromatography tandem Mass Spectrometry (LCMSMS). These methods are based on the separation of drugs on a chromatographic column followed by detection by molecular fragmentation. The formation of characteristic fragments enables a “finger-print” identification of a wide range of drugs.  Mass spectrometry identification has been tested many times in courts of law.   For a positive result to be confirmed, the drug must not only be identified by its finger print pattern but its concentration in the sample must be above the cut-off threshold recommended by the Australian Standard or outlined in the company Alcohol and Other Drug Policy.
What is the turn around time for results?
Screening test results are available within one working day from receipt of samples at PathWest Central Laboratories, Nedlands. Confirmatory results are generally available within two working days.  All results can be faxed if confidentiality is guaranteed. The preferred method of result transfer is PathWestDirect., an electronic result delivery system that is more secure than email and faster than faxing. The aquisition of LCMSMS technology at PathWest toxicology means that many confirmation results are available within one working day of the screen test.
What happens to samples which have positive results?
All samples that have a positive result are sealed and stored frozen in a locked freezer for 6 months after testing.
What is the Australian Standard for drugs of abuse testing?
The Standards Association of Australia introduced the Australian Standard (AS4308) for drugs of abuse testing in 1995.  It is designed to ensure the highest possible quality and reliability in all laboratory procedures for both the initial screen and for the confirmation test.  It recommends appropriate methods for sample collection and gives details of threshold cut-off levels for the analysis of these drugs.  Importantly, it also requires that the one laboratory carry out both the initial screening test and the GCMS confirmatory test.
Does the laboratory participate in quality assurance programs?
The laboratory is NATA accredited and participates in two external quality assurance programs.  Three external quality control samples are provided each month by the Austox program (Sydney) and the RCPA program (Adelaide). In addition, every assay batch includes blank samples as well as quality controls 25% above and 25% below the cut-off threshold limit.
What are the costs for drug testing?
Exact costing will depend on how many drugs are included in the screening procedure and on the number of samples tested.  However a screen for opiates, benzodiazepines, cocaine, amphetamines and cannabinoids would usually be in the range of $35- $50 inc. GST*. Each individual confirmatory test can be expected to range from $99 inc.GST*.  Tests for creatinine levels and adulteration are included in this cost.
Prices are negotiable with respect to testing volumes and we would be pleased to discuss rates to suit your requirements.
*Prices are subject to change or annual review. Infrequent test requests, requests from individuals and from companies that do not have service agreements with PathWest will be subject to higher costs.
Page last updated: 14 Aug 2020