We get a great number of calls every week from Real Estate Salespeople and Property Managers who have been sent a “positive” meth test result, throwing a possible purchase or rental situation into uncertainty. The main problem is that a cost-effective screening test is just that, screening. No matter what method has been used by the person doing the screening, any amount of methamphetamine detected is likely to result in the recommendation that more comprehensive (and expensive) testing be undertaken.
Here we will look at the types of screening methods used:
Field Composite Laboratory Test
This is where a several swabs are taken in different rooms around the property and these are compiled into a single sample which is sent to the laboratory. In theory the tester should not use more than 5 swabs in that one sample. The laboratory can do no more than run the sample and a calculation needs to be performed based on the number of wipes. It is assumed that IF correct sampling technique has been followed by the tester, any result less than 1.5µg/sample should indicate a PASS. Theoretically, depending on the number of wipes, a higher amount should also be a pass in some circumstances but before an opinion can be given on that, the way in which the property was sampled needs to be examined properly.
In our experience the Field Composite method results in more uncertainty than any other method and usually a whole new set of individual swabs is required to be tested if even a moderate quantity of methamphetamine is detected. We don’t favour this type of test but usually we find that the result is exaggerated overall.
Laboratory Composite Test
This method is similar to the above except that INDIVIDUAL wipe samples, each in its own tube, are sent to the laboratory. This means that the tester has taken a proper set of samples (hopefully) and recorded the details of where each was taken. The laboratory will take a small amount out of each sample and compile them into a single new sample to be run through their analysis machinery. They will not combine more than 10 samples into a single tube. The result will once again be a composite of many areas sampled and the client receives a “Theoretical Maximum”based on the number of wipes sampled. Once again the theoretical maximum can create some panic but the main advantage of this method is that the tester can ask the laboratory to run individual samples for separate results (at a cost) if more information is required. This means the tester does not need to revisit the property in most circumstances.
While Laboratory Composite tests can be confusing, overall they are the most cost effective if more in-depth results are required. We can help interpret these if the tester has done a good job with selection of areas to be tested and how they are grouped.
Presumptive In-Field Testing
These tests are designed for screening and the results are not sent to the laboratory. The tester develops the samples and provides a POSITIVE/NEGATIVE result for each sample taken. These are extremely effective in the right hands but can easily be misinterpreted by an unskilled tester.
The main advantage of presumptive testing is that they can provide an instant result that will tell us if methamphetamine is present above a certain cut-off level (usually 1.5 or 0.5µg/100cm2). Once again this is a screening result and any uncertainty should result in more rigorous individual laboratory sample testing. The general rule of thumb is that if the sample is ruled as NEGATIVE, no further testing should be needed even if traces of methamphetamine were detected at a low level.
Presumptive tests received quite a lot of scrutiny by the NZ Standards committee when they were writing the new NZS8510 standard. They spelled-out a very expensive and detailed verification process that has to be done annually by the distributors of the tests. We are yet to see if these tests can pass this scrutiny by the ESR, it may well be possible that in-field tests will only be for DIY users in the future. This would be a shame because in-field screening is a legitimate scientific technology and is extremely cost-effective in the right hands.
The Report is the Most Important Part
Often we are sent reports with nothing more than a big red exclamation mark emphasising the point that more in-depth testing is required.
Whatever screening method has been used, the results will mean nothing if not accompanied by a report that gives the client information about where samples were taken. This should involve photos, descriptions of surfaces and general information about the property. Many of the reports we are sent contain nothing of any great use and in those circumstances we can’t offer much help.
A huge number of properties tested have some amount of methamphetamine present but at low trace-amount levels. Methamphetamine is toxic but it’s not radioactive so small amounts can be tolerated. If home buyers or tenants are going to take a ‘zero tolerance’ approach then they may find themselves with few options.
The ONLY way to give a property the absolute all-clear once some methamphetamine is detected is to do a full set of laboratory results. This is expensive but there is simply no perfect cheap screening method. We favour presumptive tests if used properly to give separate results for each area at a defined cut-off level.
Feel free to call and discuss results with your local Residue Testing NZ technician, we’ve been doing this much longer than most and have pretty much seen all the likely scenarios.