Employee Drug Testing: Defending False Positive Allegations

May 21, 2021, 8:01 AM

Drug testing is increasingly complicated for employers. Per the Quest Diagnostics drug testing index, the workforce drug testing positivity rate hit its highest rate in 16 years in 2019, with marijuana drug-test positivity showing double-digit increases. Employers are navigating this increase, disability and discrimination issues, as well as state-level job protections for some medical and recreational marijuana use.

Regardless of the complexity posed by these changes, one thing remains the same: People will fail drug tests and sue, claiming that they never used drugs and that the administered drug test was faulty and/or discriminatory.

Often such a suit is brought after an employee or applicant fails one drug test and then passes a second drug test that they secured on their own. This article offers some helpful tips in defending against such claims.

First Steps

First, it is important to establish whether the employee or applicant is claiming that he or she was exposed to drugs in the environment. This is typically a claim of exposure to secondhand smoke, or living with a drug user, but it is also sometimes claimed by a law enforcement officer who interacts with drugs in the course of his or her employment.

Often, the plaintiff in false-positive drug testing cases will specifically disavow any exposure to drugs. That is a helpful fact, because then the presence of any drug in their system—particularly in the second test—is persuasive evidence of intentional illicit drug use.

Second, a second drug test often provides evidence that supports the results from the first drug test, even where the second drug test is legitimately interpreted as negative. Specifically, the second drug test often shows evidence of drugs below, sometimes just below, the laboratory cutoff and/or more than spiked control samples run through the drug testing laboratory process. (Such samples—with known drug levels—are tested to verify that the laboratory process is working correctly.)

In the absence of environmental contamination, there is no legitimate explanation for the presence of drugs in the second drug test, meaning that the second negative result supports the first positive result. As drug-testing laboratory directors love to say, “a negative test result does not necessarily mean that no drug was present in the sample.”

Where the drug test at issue in the litigation was run as part of a batch of drug tests, a chart showing the cutoff used, the drug levels yielded by the testing of various laboratory control samples, and the results of all the drug tests run in the batch at issue can be a very helpful way of showing why the plaintiff’s second negative drug test is actually a confirmation of the first positive drug test. Typically, the plaintiff’s sample is near the cutoff and/or distinct from the bulk of “no-drug” samples depicted on the chart.

Third, even the absence of finding any drug in the second sample, there are often legitimate reasons why the second sample was negative—reasons that do not call into doubt the scientific validity of the first drug test. The time delay between the first and second drug test is often the explanation for why the sample donor failed the first test and passed the second drug test.

With a time delay, the negative second test ordered by the plaintiff is often merely the result of drugs dissipating out of the donor’s system. This is a particular risk in urine drug testing given the short half-life of drugs found in urine and given the ease with which a sample donor can flush his/her system with water.

Additionally, comparing one drug test modality to another drug test modality (hair to urine, oral fluid to urine, etc.) is typically an apples-to-oranges comparison–particularly because of different “look back” periods.

For example, hair drug testing typically identifies drugs used in the seven to 90 days prior to the test. Urine and oral fluid drug testing typically identify drugs used much more recently, but do not look back nearly as far as hair drug testing.

Even when the same modality is used (urine compared with urine, etc.) different laboratories use different technologies and methodologies in their testing process. The natural and legitimate variation in results caused using different technologies can often explain the “discordant” results between two drug tests.

Claims Another Substance Caused a Positive Result

Finally, employers routinely face claims in litigation that some other substance (prescription drugs and CBD, but also mentholated vapor inhalers and even poppy seed bagels) caused a “false positive” drug testing result.

Fortunately, here employers can rely on their drug testing medical review officer (MRO) to ferret out the legitimacy/illegitimacy of such claims by interviewing the donor, securing copies of prescriptions, evaluating the laboratory results, etc. Know that MROs have the skill and experience to undertake such an analysis; employers should rely on that and not try to make such decisions themselves.

Employers should also be aware that prescription drugs and CBD use often tee up disability discrimination issues that should be managed through an informal interactive dialogue between the employee and HR to discuss reasonable accommodation of an employee’s disability.

Similarly, medical and sometimes even recreational marijuana frequently carry job rights that require an Americans with Disabilities Act-like dialogue. Note that the ADA itself does not provide any protection for medical marijuana since marijuana is still illegal under federal law; the dialogue is required for state ADA analogs like the New Jersey Law Against Discrimination, Massachusetts’ Chapter 151B, etc.

Drug testing is an area of rapid change in employment law. All kinds of drug testing-related lawsuits, including “false positive” claims, are being filed in ever-increasing numbers. Even in this brave new world, however, sophisticated employers can defend their drug-free workplace policies and defeat such claims.

This column does not necessarily reflect the opinion of The Bureau of National Affairs, Inc. or its owners.

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Author Information

Michael K. Clarkson, shareholder in Ogletree Deakins’ Boston office and co-chair of the firm’s Drug Testing Practice Group, works regularly with employers and is a leading voice on critical drug testing issues. He drafts compliant drug testing policies, advises on drug testing issues, and defends employers against “false positive” drug testing claims.

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