By Diane Zwirecki


As a responsible employer, you’re obligated to protect your employees’ health and safety and anyone with whom they come in contact. That’s reason enough to ensure that your job candidate drug screens are watertight. The ongoing crisis of opiate abuse and the increasing legalization of marijuana have emphasized the importance of pre-employment drug testing across the nation.

With the expansion of the number and types of drugs included in pre-employment screens comes a greater need to be aware of the potential for false-positive results. Because yes, they do happen. But you can take measures to minimize them.

Innocent Triggers

In some cases, a drug test may report the presence of illicit drugs, even though none were taken. Triggers include certain foods, regularly used medications, and other products. Common examples and the drugs for which a false-positive report may result include:

  • Ibuprofen – marijuana, barbiturates or benzodiazepines.
  • Cold or hay fever remedies, nasal decongestants, or diet pills – amphetamine.
  • Sleep aids – barbiturates.
  • Antidepressants – benzodiazepines.
  • HIV medication – marijuana.
  • Antipsychotic drugs – methadone or amphetamine.
  • Coca tea – cocaine.
  • Poppy seeds – marijuana.

Mouthwash containing ethanol, a form of simple grain alcohol, can also trigger a false positive, as today’s best screens can detect even trace amounts. Notable in light of the ongoing COvid-19 pandemic is that the same can happen with alcohol-based hand sanitizers if used regularly.

Second-hand marijuana smoke also may be a culprit, causing traces of THC to show up in urine. The chances are low that there would be enough of the chemical in a person’s system to trigger such an outcome, but a second test can be done for confirmation purposes.

How to Avoid False Positives

Five and 10-panel drug tests use paper strips impregnated with antibodies that react in the presence of a drug or its metabolites – substances produced when a drug breaks down in the body. Also known as immunoassays, panel tests detect drugs much the same way home pregnancy tests change color in the presence of pregnancy-related hormones.

  • Panel tests are highly effective but may occasionally be subject to false positives. These occur when a substance in a specimen is chemically similar to the target substance. Even as test materials makers continually refine the sensitivity of panels to reduce the likelihood of false positives, the vast and growing number of substances that can masquerade as illicit drugs means false positives will not completely go away, at least in the near future.
  • Labs can re-test specimens to rule out the possibility of a false-positive result. Extremely precise and sensitive methods are used, typically spearheaded by a medical research officer (MRO) – a physician with specialized expertise in substance abuse and drug testing. In cases of positive results, the MRO will follow up and, based on their findings, may declare an accurate positive test result false if it detects a medically legitimate drug.

When you work with Chane Solutions, the results of every pre-employment and drug screening test you order undergo a thorough quality control audit to ensure the highest possible degree of accuracy. If there is ever a question about results, we don’t stop until we’ve confirmed the right answer. We have a well-earned reputation as a leader in our field – and we’re committed to developing customized solutions for your business. Contact us today to learn more.