A drug test consists of subjecting the sample taken from you to various chemical processes. In case of urine testing, your urine sample is tested with three different reagents, each of them responsible for identifying a certain type of drug metabolite.
In the case of a hair drug test, your hair follicle will need to be removed from your scalp (or other body part). Learn more about the hair drug test and ways you can pass it.
The first reagent is an IGG antibody, capable of identifying the metabolite. The second is made with G6PD (Glucose-6-phosphate dehydrogenase) that tests for the presence of this enzyme associated with the metabolite, and with NAD+ (Nicotinamide Dinucleotide). The third reagent contains G6P (Glucose-6-phosphate), which doesn’t actually play a role in identifying drug metabolites, but it supports the chemical processes needed for the success of the test.
Metabolites are used for control testing, too. Basically the lab adds the metabolites they have there, so it can compare the results, when the urine sample is tested. If the test reveals that the antibody mentioned earlier interacted with the metabolites found in the donor’s sample, which is you, this means that the result of the test is positive. If, on the contrary, it interacts only with the metabolite introduced by the lab, the result is negative. The latter is attached to
G6PD, so the antibody blocks it, in case of a positive result, and thus, the antibody can no longer interact with the metabolite introduce by the lab.
What does a positive result mean?
If the result of the test is positive, it means that the antibody interacted with the metabolite from the donor’s sample and any further interactions are blocked. What happens next is that the second reagent allows the NAD+ to bind and transform into NADH. The latter is responsible for turning the sample into a specific color that can be measured with the means of a spectrometer. The color resulted is absorbed by light at a certain speed, and this is what the spectrometer will determine. This way, the lab will be able to tell if the test result is positive.
With the help of highly technological devices, the lab can tell if your urine sample returned a positive result when tested. The spectrometer confirms if the result of the test is positive, under the circumstances described above.
In case you are among those who get a positive result when tested, a good idea is to already have a course of action set in place. Here are some things you can do:
- Ask for a retest
- Be prepared to pay for the second test
- Ask for another test within one hour
- Especially if you have been tested for at least one year with no such results, it is highly indicated to be ready for such occurrences.
What do false positive results mean?
There are situations when the results of a drug test are considered false positive results. What does this mean? Practically, it means that another compound is responsible for the positive result, and not the drug; for instance, consuming poppy seeds may lead to positive drug test results for consumption of opiates, even if the donor is clean.
The gas chromatography/mass spectrometer test can make the difference between consumption of such compounds, like ibuprofen and poppy seeds that can lead to false positive results.
If that is the case, and the donor is absolved of any traces of doubt, after the GS/MS test, the employer can go ahead and hire the respective person without any worries.
What do negative results mean?
If the urine sample is completely clean of any traces of drugs, then the antibody will not be able to interact with the metabolites in the sample. Instead, it will bind with the one provided by the lab, and after that, the NAD+ will not be able to turn into NADH, which means that the results will be negative for drug use.
What complications can appear?
Drug screening is not exactly a black and white procedure. Each screening requires the presence of a medical review officer (MRO), who will be in charge of examining the results and conduct an interview with a donor to establish whether the results of the test are accurate or not. This happens especially because drug tests can return different results that cannot be all true at the same time.
What does a non-contact positive result mean?
As mentioned earlier, the results sent back by the lab are not consistent, they need to be reviewed by an MRO. If one of the results is positive, the MRO will try to contact the donor and conduct an interview.
During this interview, the MRO will ask for documents or other information to infirm the positive test. If such proof is identified, the result of the test can be turned to negative. Only if the donor cannot be found, the final result of the test is named a non-contact positive.
When do labs reject samples?
A sample must be kept in certain conditions so it doesn’t become contaminated. A damaged sample will be rejected by the lab, as testing cannot be conducted under the circumstances. Some damage can be alleviated by the use of an affidavit, but there are cases when nothing can be done, and the lab will require another sample for testing.
When do test cancellations occur?
Drug tests can be cancelled in case the lab identifies or suspects some kind of chemical interference between the sample and other compounds. The MRO is entitled to ask for an observed sample, in such cases.
This is a practice that is not necessarily seen as an attempt to cheat a drug test, because it can accidentally happen. Drinking lots of water before a urine drug test can change the physiological composition of the sample, so the lab will not be able to clearly identify traces of drug, in case drug use took place. The usual course of action involves the lab asking for another sample, this time with the advice to avoid drinking too much water, coffee, or exercising too much, all practices that can dilute the composition of the urine.
If someone continues to provide urine samples that show signs of dilution cannot be fired, since no clear intention to cheat the test can be established. However, those who are seeking employment can only provide two samples, and if both are diluted, they may not get hired.
Changes in temperature
An abnormal temperature of the urine sample also makes it inadequate for testing. Asking for a retest is usually what happens next.
What can cause invalid results?
There are many situations that can lead to invalid results. The most common are:
- The appearance of the sample makes it unsuitable for being drug tested
- Valid results are impossible to obtain, and no cause can be clearly identified
- The results cannot be confirmed due to unknown substance interference
- Invalid results involve the MRO, who must reach for the donor and ask for an interview.