This from www . medicalobserver . com . au:
The dope on drug tests
5 October 2007
Doctors are increasingly being asked to order drug tests for third parties, but what are the legal implications? Dr Kathy Kramer reports.
GPs may find themselves ordering a urine drug screen in a variety of situations, according to Dr Nick Demediuk, a member of the RACGP’s Victorian faculty board.
These include checking for polydrug use in patients on drug programs, pre-employment screens, insurance check-ups, compliance testing and court orders.
And it looks like it’s becoming increasingly common, according to Sydney GP Dr Dennis Grinius.
“I remember doing a drug screen where the patient denied using drugs. He had had a car accident and needed to be tested for cannabis. I ran a full drug screen… and it came back positive for everything, to everybody’s surprise.”
He has also recently done drug screens for an employment medical, as a condition of a patient’s probation, and for an insurance medical.
But as Dr Demediuk warns, if a third party – such as a potential employer – is involved, there is a potential issue with privacy and confidentiality.
“No test should be performed without the patient’s knowledge, no matter what it is,” says Andrew Took, Avant’s national manager of medico-legal advisory services.
“The more controversial the test, the more the requirement is for informed consent.”
When it comes to employer-requested tests, “a patient must specifically consent to having a drug screen done, because there may be consequences for their career if the result is positive”, he says.
“A patient may refuse drug testing as part of the examination, and these tests should never be done when the patient refuses. Drug testing should not be done as a matter of course – either the patient or the employer [with the patient’s consent] must specifically ask for drug screening.”
It’s wise to deal with the issue of releasing information – whether that’s from a physical examination or laboratory testing – to third parties before you do the check-up, Mr Took advises.
Specifically ask if all findings can be passed on, regardless of the test result, or if the patient wants to review the information first. And always document the patient’s response.
When dealing with young people, it’s a good idea to ask specifically about the possibility of a positive test for cannabis and get their express consent for cannabis testing, Mr Took recommends.
In addition, he says GPs have a duty of care to offer treatment if there are positive findings, such as a positive drug test result. This includes people who are not regular patients but have come simply for the check-up.
“If they don’t want treatment, you should explain the need for medical help and offer to refer them or to write a letter to their regular GP – explain why the result means you have concerns. If they refuse treatment, document that.”
Common drug screens
Some drugs that can be screened for (what is included on a “routine” screen may vary at different labs):
Interpreting drug tests requires some caution. As Dr Demediuk points out, there is usually a threshold that must be reached for a test to become positive; cross-reactivity with drugs taken for quite legitimate reasons may occur; and the timing of the sample may have an effect.
- benzodiazepines, including alprazolam, clonazepam and lorazepam
- amphetamine-type substances, including MDMA (ecstasy)
“Cannabinoids remain positive for weeks but heroin is cleared very quickly, so you have to have some idea of the pharmacokinetics before you make assumptions about whether it’s been recently used or recently not used.”
Also, patients may try to “trick the system”, he warns, so sometimes supervised samples may be necessary.
“For example, they may dilute the sample with tap water, or use somebody else’s sample, or drink a lot of water to dilute their urine.” Dilution can be tested for by checking creatinine levels in urine.
Peter Bowron is a senior scientist with the Toxicology Unit, PaLMS (part of Northern Sydney Central Coast Health), a laboratory with extensive experience in drug testing.
“Laboratory testing is a multi-stage process. Negative results from preliminary screening are usually reliable within the limitations of the test, but positive results call for re-testing from the original sample using a more specific methodology. Sometimes multiple methods are used.”
HOME testing kits are available for testing urine, hair, breath and saliva.
However, a review article in Pediatrics concluded home tests were of little value, as it’s hard for parents to know which test to choose, how to collect a sample properly, and how to interpret the results.
There are also kits testing for drugs in the environment, such as children’s bedroom drawers.
“This is a little bit like point-of-care testing. It doesn’t necessarily tell you what the person is taking, and I don’t know how sensitive they are or what the level of false positives may be,” says Peter Bowron, a senior scientist with Sydney’s PaLMS laboratory.
“They probably don’t have a great deal of use.”
Fortunately, this sort of home testing doesn’t happen on a large scale in Australia, the RACGP’s Dr Nick Demediuk believes.
There is no simple process that can identify all drugs.
Routine screening involves a range of commonly abused substances, both illicit and therapeutic, such as cannabis and benzodiazepines. But drugs not on the list – such as GHB – can often be checked for if a request is made.
Urine is the preferred fluid used: most drugs are concentrated and excreted in urine; it’s safe and easy to get an adequate sample; the window of detection is wide; and the results are qualitative, so levels are not given.
Point-of-care testing is another option, with kits testing for cannabis, opiates, amphetamines, cocaine and benzodiazepines, Mr Bowron says. “A negative result is reasonably good, but if you had a positive result you’d have to send the sample on.”
For example, a positive for morphine could occur following pholcodine or codeine ingestion, while ranitidine can give a false positive result for amphetamines.
From a medico-legal viewpoint, the important issues in drug testing are to get fully informed consent from the patient, to document under what circumstances information can be released to third parties, and to offer treatment following a positive result.