Making Sense of Drug Tests and False Positives

It’s becoming increasingly common for employers to implement drug testing policies for candidates and employees. Drug testing is a vital component of creating and maintaining a safe workplace. However, it’s important to acknowledge that false positives, while not widespread, do occasionally happen. Let’s take a closer look at what might cause a false positive and how best to respond.

The Value of Drug Testing

It’s worth taking a moment to examine the many ways drug testing protocols provide value to organizations.


Employees impaired by drugs or alcohol pose a significant risk. The likelihood of accidents, driving violations, mistakes, and injuries increases when alcohol and drug use is present.


Along with the increased risks comes increased liability. If your employee causes harm to other employees, clients, customers, or the public while under the influence, you expose your organization to potential legal repercussions.


Employees who use illegal drugs and misuse or abuse alcohol are more likely to commit other crimes at the workplace such as theft or embezzlement. Keeping your workplace free from drugs and alcohol also protects your reputation and your brand.

The Bottom Line

The bottom line about workplace drug testing involves your bottom line: the costs of not testing for drug use far outweigh the costs associated with implementing a drug testing program.

The Process

Drug testing begins when a sample is collected. Hair, blood, saliva, and urine samples can all be used for drug testing. Samples are processed by a lab. Each sample is divided in half; one half is tested and the other is reserved for retesting or resolving challenges.

Drug tests can detect a wide range of substances and employers can define what screens they’d like to run. Local laws, industry regulations, and even the drug climate in the area will direct the choices. That said, most employers opt to run a 5-panel or a 10-panel test.

Five-panel tests check for the following:

  • Amphetamines
  • Cocaine
  • Opiates
  • Phencycladine (PCP)
  • Marijuana (THC)

Ten-panel tests add the following:

  • Barbiturates
  • Benzodiazepines
  • Methadone
  • Methaqualone
  • (Darvon)

A common addition is to screen for oxycontin and oxycodone specifically, since abuse of these medications is so predominant and are often not detected by standard opiate tests.

What Causes False Positives?

False positives occur when the immunoassays used to detect specific substances encounter substances that are chemically similar. These imposter substances are often byproducts of over-the-counter meds, foods, or supplements. While drug testing technology is constantly getting more precise and more sensitive, false positives remain an issue. Because of this, most labs retest positive specimens using testing methods that are far more sensitive.

How to Respond

When a positive test is returned, a physician at the lab will reach out to the subject to collect information about anything that might have caused a positive result. With the help of the tested specimens and this info, the physician will certify the result as either a pass or fail.

Individuals may dispute positive results. Their recourse varies from state to state, but one option is that the saved half of the original specimen be tested.

In Sum

False positives do occur, but a careful employment drug screening policy and a certified drug testing partner will minimize their impact.

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