September 6th, 2024 | Sterling

When Employee Drug Test Results Aren’t Negative

After interviewing several job candidates, you’ve finally found someone who seems like the right fit for the role and your company culture. Plus, their background check came back spotless. Just when you thought you found your company’s next great team player, the drug test comes back positive.  

Could an Employee Drug Test Show a False Positive Result? 

Today’s candidate and/or employee drug testing methods are highly effective for identifying unmanaged substance abuse problems of job candidates and current employees. If your organization’s drug-free workplace policy reflects industry drug testing best practices, the chances of your candidate or employee experiencing a false positive drug test — or a test that shows the presence of a substance that hasn’t been taken — is almost zero percent.   

However, the possibility of false positives comes into play when a drug testing program is solely based on instant or point of collection tests. Confirmation testing using established cutoff thresholds and review of results by a certified Medical Review Officer (MRO) are critical components of an workplace drug testing service that delivers reliable and thorough results. They are key elements in your drug-free workplace program that help you maximize your effectiveness in building and maintaining a safe and productive work environment for your employees. 

To better understand the importance of these best practices, let’s walk through the process of drug testing for employees in greater detail. 

The Initial Drug Screening 

A workplace drug test begins with an initial qualitative screen of the collected specimen using an immunoassay test. Instant or point of collection tests are examples of immunoassay tests. They use specific antibodies to detect common drugs of abuse or their metabolites. One problem with immunoassay screening, however, is that false positives can result from medications or foods that have similar chemical structures. This is why immunoassay tests should be only the first step when the initial drug test result is not clear.  

Confirmation of the Drug Test Result 

When the initial immunoassay screen is not negative, a laboratory-based confirmation test (such as a gas chromatography/mass spectrometry (GC/MS) or liquid chromatography/mass spectrometry (LC/MS) test) should be used to confirm the presence of the specific drug and determine the positive result. GC/MS and LC/MS testing is considered highly accurate, sensitive, and reliable, and these tests can distinguish between structurally similar compounds in the urine sample. To confirm instant or point of collection test non-negative results, employers can either send the test device to the laboratory for confirmation of results (if the device is set up for lab-based testing) or order a lab-based drug test through their preferred clinic network. Either approach will validate the immunoassay screening through a much more specific laboratory test that can positively identify the substance that triggered the non-negative result. 

What Are Cutoff Levels for Drug Tests?  

Cutoff levels are the set concentration (usually nanograms per milliliter, or ng/mL) of a specific controlled substance that can be present in the sample to trigger a positive result. Samples with substance concentrations under the cutoff are reported as clear. Federally regulated tests must use the cutoff standards established by the U.S. Department of Health and Human Services (HHS). Employers who aren’t federally regulated are not required to adhere to HHS standards. However, many do follow the HHS cutoffs for drugs on the 5-panel test because they are considered best practice in the industry, and since they are used for regulated testing, are more defensible if challenged by a candidate or employee. 

Lab-based HHS Cutoff Levels, 2024 

SAMHSA, 2024 

As seen above, HHS standard cutoff levels can be different for initial tests and confirmation tests, depending on the substance. Detection cutoff levels are used by testing laboratories to help reduce false positive testing results. As an example, in 1998, the Department of Health & Human Services (HHS) raised the cutoff levels for opioids from 300 ng/mL to 2000 ng/mL to avoid false positives that can result from poppy seed ingestion. As a result, false positives from poppy seeds are relatively rare.  

Further Minimizing Positive Drug Test Results for Valid Reasons 

Even with lab-based confirmation testing, however, a positive result can sometimes still occur for legitimate reasons. Despite the raised cutoff levels, the consumption of poppy seeds can still produce positive results for opiates depending on the nature of the poppy seeds consumed and how they are prepared.  Use of hemp-containing foods like CBD, which can contain some tetrahydrocannabinol (the psychoactive ingredient in marijuana) can result in detection of marijuana. 

Some prescription and over-the-counter drugs have chemical structures like other drugs and can cause false positive results. For example, over-the-counter cold medications and some antidepressant medications can trigger false positive results for amphetamines or benzodiazepines. Some antibiotic and HIV medications can produce false positive results for opiates. 

The Role of the Medical Review Officer 

With the potential that legitimate candidate or employee actions could contribute to a positive drug test,  including a certified Medical Review Officer (MRO) — a licensed medical physician with separate qualification in substance abuse testing — in your workplace drug testing service is essential. If your drug testing program is under federal regulation, or your testing is performed in certain US states, it is mandatory. 

The MRO reviews and properly interprets drug test results reported by the testing laboratory, evaluates medical information presented by the candidate or employee, and determines if a legitimate medical reason exists to explain the non-negative result. If the MRO review uncovers a potential legitimate reason for the results, they can order additional tests to help confirm the substance causing the positive drug test.  

As an integral part of your drug testing program, the MRO helps support your drug testing program by: 

• Verifying medical information provided by the candidate or employee to explain a non-negative result, increasing testing validity. 

• Protecting the confidentiality of the candidate or employee’s medical information. 

• Providing an avenue for dispute of final test results if the candidate or employee requests a re-evaluation. 

• Assisting in compliance with applicable regulations, result reporting requirements, and federal standards for legal use of substances. 

An MRO is also critical for evaluating dilute results, tests that may be suspected of adulteration or substitution. Negative dilute specimen can result from a variety of sources not associated with drug abuse, including as an outcome of medications taken by the candidate or employee, unregulated health issues, or even by accident. An MRO can review potential causes for dilute results and help ensure the test results are determined according to your company’s drug policy guidance or, if the test is regulated, according to federal guidelines. 

Take Aways 

Regulations and best practices for employment drug testing are ever-changing, creating a challenging environment for employers seeking to maintain a safe and productive workplace. Including confirmation testing with established cutoff levels and a qualified MRO in your program are two important steps you can take to strengthen your company’s drug testing program. To check that your workplace drug testing program is as effective as possible, you should regularly review your drug testing policy with qualified legal counsel.  

Please  reach out to Sterling with questions or concerns; our Drug & Health Screening experts are ready to assist.  

Sterling is not a law firm. This publication is for informational purposes only and nothing contained in it should be construed as legal advice. We expressly disclaim any warranty or responsibility for damages arising out this information. We encourage you to consult with legal counsel regarding your specific needs. We do not undertake any duty to update previously posted materials.