Why do initial drug tests need to be confirmed?

By Suzanne Ball | Last updated: January 17, 2019

When companies implement a workplace drug-testing program, it’s important to include a policy regarding how any positive results on the initial screening will be handled.

Drug testing may be done for a variety of reasons: Pre-employment, random, reasonable suspicion, return-to-duty, and post-accident are common situations. Testing is most commonly performed with urine specimens, but hair, saliva, and blood may also be used.

After collecting the specimen, the sample is divided into two parts, and sent to the lab. This is called a split specimen.

The first half is used for the initial drug testing. If results are negative (no drugs are detected) then testing is complete and the employer is notified. If results are positive, indicating the possible presence of one of the drugs, a portion of the first sample is used for further testing. Similarly, if the drug test is performed on-site, if there are no drugs detected, then the test is complete and the employer is notified. If the presence of drugs is detected, then the sample is split and sent to the lab for further testing.

Confirmatory testing is performed by Gas Chromatography/Mass Spectrometry (GC/MS) at a DHHS/SAMSHA-certified laboratory to focus on and quantify the specific drug identified by the initial testing. Cutoff rates have been established to maintain consistent reporting; they are listed in the Federal Register.

Confirmatory testing is an essential component of a workplace program for several reasons:

  1. GC/MS results from a certified laboratory are considered solid evidence in court if an employee contests the drug screening results.
  2. Both employer and employee are protected when an initial positive result is sent to a certified lab for confirmation. Although false positive results on initial screening are rare, they do occur. With conclusive data from a confirmatory test, the employer can legally proceed with the company’s policies regarding positive results. For the employee, a confirmatory negative result means that no further action can be taken.
  3. A Medical Review Officer (MRO) is a physician who reviews the results of all confirmatory tests. The physician is trained and certified in analyzing laboratory tests. If the test is negative, the physician signs off on the results. If positive, he/she notifies the employee to discuss the results. For example, if the results show presence of an opioid, the employee may be able to provide proof of a prescription at the time of the screening. This adds an extra layer of protection in the process.

With confirmatory testing, employers can implement and maintain workplace policies regarding drug testing with confidence. Employees can be assured that testing is conducted without bias.

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Written by Suzanne Ball

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Suzanne Ball is an experienced Registered Nurse with a Masters Degree in Health Sciences. She has worked in a variety of settings, including acute care, quality improvement, and research. She is a freelance writer who specializes in writing about medical and health topics.

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