What is a Non-Negative Drug Result?

We are often asked, what is a non-negative drug test result? This can occur during the drug screening phase of the drug test process. The screening phase utilises immunoassay technology. As a result, we can detect the presence of a drug group’s metabolites in a given sample. Usually a urine or saliva sample. If we don’t detect metabolites of the drug group in the sample, then the result is deemed negative. In other words, this would be classed as a pass.


However if we do detect the metabolites of a drug group we screen for, this would be deemed as non-negative. So you might ask, why isn’t this classed as a positive result? Well, it is because of the nature of immunoassay screening. In drug screening, this science is based on ‘binding’. In other words, if the drug groups metabolites are present in the sample, the reagents will bind with the saliva or urine. Conversely if the metabolites are not present in the sample, then the reagent will bind with the drug strip within the device. This is how we interpret the results from the lines that appear or do not appear on the drug strip.


How medication affects a drug test

So back to the question. Because of the nature of immunoassay, medication can also influence the result of the drug screen. For example, medication with a similar molecular structure for the drugs we screen for, could produce what we call a false positive result. So it is because of this chance of a false positive or even false negative result, that we cannot class the result as a positive or a fail at the screening stage.


This is why instant point of care drug screening should not be used for any legal or disciplinary purpose. Non-negative drug samples should always be sent for laboratory confirmation. The full laboratory drug test will confirm and quantify the presence of any illegal or controlled drug. Call and speak to a Clinical Advisor today. They will explain point of care drug screening in detail and help you choose the right test for your situation.