What Is MRO Review in Drug Testing?
When a drug test comes back positive, invalid, or questionable, the result usually does not go straight to an employer or court. Instead, it goes through a process known as MRO review.
An MRO, or Medical Review Officer, is a licensed physician responsible for interpreting laboratory results and determining whether there is a legitimate medical explanation for a finding. This step helps ensure accuracy, fairness, and confidentiality in workplace and legal drug testing programs.
Understanding how MRO review works is important for employees, employers, HR professionals, and anyone subject to regulated testing.
This article explains what MRO review in drug testing means, how the process works, what individuals should expect, and how final results are determined.
What Is a Medical Review Officer (MRO)?
A Medical Review Officer is:
- A licensed physician
- Trained in substance use disorders
- Certified in drug test result interpretation
The MRO acts as an independent safeguard between the laboratory and the organization receiving the results.
Why MRO Review Exists
Laboratory testing is extremely accurate, but it cannot determine why a substance is present.
For example:
- Was there a prescription?
- Was medical treatment involved?
- Could there be another legitimate explanation?
The MRO’s role is to investigate before a result is finalized.
When Does an MRO Get Involved?
An MRO typically reviews results that are:
- Positive
- Refused
- Dilute
- Invalid
- Adulterated
- Substituted
Negative results usually pass through automatically without contact.
What Happens During MRO Review?
The process usually follows several steps.
1. Laboratory Reports Result to the MRO
The lab sends findings to the physician rather than the employer.
2. MRO Contacts the Donor
If needed, the MRO or their staff reaches out confidentially.
3. Medical Explanations Are Evaluated
Prescriptions or treatment records may be requested.
4. Final Determination Is Made
The result is verified, changed, or clarified.
Is the MRO on the Employer’s Side?
No. The MRO is meant to be neutral and independent.
Their responsibility is to:
- Protect donor rights
- Maintain program integrity
- Ensure accurate reporting
What Might the MRO Ask For?
If contacted, individuals may need to provide:
- Pharmacy information
- Prescription numbers
- Physician contact details
- Medical documentation
Prompt cooperation is important.
How Prescriptions Affect Results
If a person has a valid prescription consistent with the detected substance, the MRO may verify the test as negative (depending on policy and regulations).
However, this varies by program.
What If There Is No Legitimate Explanation?
If the MRO cannot confirm a valid reason, the result is typically verified as:
Positive
The MRO does not determine discipline—only the accuracy of the finding.
What Happens If the MRO Cannot Reach the Donor?
If contact attempts fail within required timelines, the result may be verified based on the laboratory data.
It is critical to respond quickly.
How Long Does MRO Review Take?
Often:
- 1–3 business days
Complex cases may take longer if documentation is required.
Is MRO Review Required for All Programs?
MRO review is mandatory in many regulated environments, including:
- DOT drug testing
- Federal safety-sensitive programs
It is also widely used in non-regulated workplace testing.
Confidentiality in MRO Review
Medical information is kept private.
Employers typically receive only:
- Verified result status
Not diagnosis or treatment details.
Can the MRO Change a Positive Result?
Yes, if legitimate medical evidence supports it.
This is one of the most important protections in the testing system.
What the MRO Does NOT Do
The MRO does not:
- Decide employment actions
- Provide treatment
- Offer legal advice
- Share unnecessary medical data
Their role is strictly result verification.
What If Someone Disagrees With the MRO?
Procedures may allow:
- Split specimen testing
- Review of documentation
- Employer or legal appeal routes
Options depend on the testing program.
MRO Review in DOT Testing
DOT rules are especially strict.
Even with a prescription:
- Some medications may disqualify safety-sensitive duties
- Employers may need additional medical clearance
Invalid, Dilute, and Adulterated Results
The MRO also handles unusual findings like:
- Too much water
- Abnormal chemistry
- Signs of tampering
The physician determines next steps.
Why MRO Review Builds Trust
Without this step:
- Legitimate prescriptions could be misinterpreted
- Errors could harm careers
- Privacy might be compromised
The process creates balance.
What Employees Should Remember
If contacted:
- Respond promptly
- Provide accurate information
- Follow instructions
Delays can complicate outcomes.
What Employers Should Understand
Employers should:
- Wait for verified results
- Avoid acting on lab screens
- Respect confidentiality
Premature action can create legal risk.
Common Misconceptions
Myth: The lab tells my boss I’m positive
Reality: The MRO reviews first
Myth: If I have a prescription, I won’t hear from them
Reality: Verification may still be needed
Myth: The MRO decides punishment
Reality: Employers do
Why MRO Review Is a Critical Step
It ensures:
- Fairness
- Accuracy
- Legal defensibility
- Protection of medical privacy
Frequently Asked Questions
Q: Will the MRO call for every test?
A: Usually only for non-negative or unusual results.
Q: How fast must I respond?
A: Typically within the timeframe given, often the same day.
Q: Can I refuse to speak to the MRO?
A: Refusal may result in verification based on lab data.
Summary: What Is MRO Review in Drug Testing?
MRO review is a physician-led verification process that ensures drug test results are accurate and fairly interpreted. It allows individuals to present legitimate medical explanations before employers or courts receive a final report.
Final Thoughts
Drug testing programs are designed to balance safety with individual rights. The Medical Review Officer plays a key role in maintaining that balance by providing expert oversight and protecting confidentiality.
Understanding how MRO review works helps reduce anxiety and supports smoother outcomes for everyone involved.
