A call from a Medical Review Officer (MRO) can be unsettling, but it is a standard part of the workplace drug testing process. The MRO is a licensed physician with specialized training in toxicology and federal drug testing regulations who acts as an independent medical expert. Their primary function is to receive and review laboratory results and determine if there is a legitimate medical explanation for any result that is not clearly negative. This process is in place to prevent a common medication or an unknown medical condition from unfairly affecting your employment status while protecting confidentiality.
The Role of the Medical Review Officer
The Medical Review Officer is an impartial “gatekeeper” whose mandate is to ensure the fairness and accuracy of the drug testing program. They are not an employee of the company that ordered your test, but rather an objective authority tasked with applying medical expertise to laboratory data.
The MRO’s responsibility begins when the laboratory reports a result that is not a simple negative, such as a preliminary positive, adulterated, substituted, or invalid specimen. They meticulously review the Chain of Custody documentation to verify that the collection and testing procedures were followed correctly without any fatal errors. Only after confirming the integrity of the process will the MRO initiate contact with you, the donor, for a confidential medical interview.
The Specific Reasons for MRO Contact
The single most frequent reason an MRO will call is to discuss a preliminary positive result for a substance that can be legally prescribed. Many common prescription drugs, and even some over-the-counter medications, contain compounds that are chemically similar to illicit substances and can trigger a positive reading on the initial screen. The MRO needs to conduct a confidential interview to determine if a valid prescription covers the presence of the detected drug or its metabolites.
For example, a test might be positive for amphetamines, which could be due to a prescription for Adderall, or it could be positive for opioids, which may be explained by a recent surgery requiring pain medication. During this call, the MRO is obligated to verify the existence and legitimacy of your prescription with your pharmacy or prescribing physician. If the prescription is verified and the dosage is consistent with the level found in your specimen, the MRO will change the final result reported to your employer to a “Negative.”
Contact may also be initiated if the laboratory flags your specimen for validity concerns, classifying it as adulterated, substituted, or invalid. An adulterated specimen contains a foreign substance intended to mask the presence of drugs, while a substituted specimen has characteristics inconsistent with human urine. The MRO must investigate whether this anomaly is due to deliberate tampering or a physiological condition like a kidney disorder or excessive fluid intake.
Employees in safety-sensitive positions, particularly those regulated by the Department of Transportation (DOT), face additional scrutiny, and MRO contact is mandated for any non-negative result under strict federal guidelines. To resolve the issue quickly, you should have the prescription number, the name of the prescribing physician and pharmacy, and the date the prescription was filled available for the MRO during the call.
Potential Outcomes Following MRO Review
After the confidential discussion and verification process is complete, the MRO will issue one of three primary final determinations to your employer. The most favorable outcome is a Negative result, which is reported when the MRO successfully verifies a legitimate medical explanation for the preliminary positive finding. Crucially, in this scenario, the employer is only told the test was negative and is never informed about the specific medication or medical condition involved.
The MRO reports a Positive result if no valid medical explanation is provided or verified for the presence of the prohibited substance. This final determination is made only after the MRO has exhausted all reasonable efforts to contact you and conduct the necessary medical interview. Similarly, if the MRO determines the specimen was adulterated or substituted, this is reported as a Refusal to Test, which carries the same severe consequence as a verified positive result.
A test may also be reported as Cancelled or Invalid if the MRO finds a fatal flaw in the collection or testing procedures that compromises the integrity of the sample. In this case, the employer is notified and typically required to have you undergo a retest. Failing to return the MRO’s calls within a reasonable timeframe, often 72 hours, is typically treated as a refusal to cooperate and is equivalent to a refusal to test determination.