The Role of the Medical Review Officer

A Medical Review Officer is a physician who independently reviews laboratory drug-test results and relevant medical information before an authorized final result is reported. The MRO helps separate analytical detection from the legal and medical interpretation required by a testing program.

Qualifications and independence

DOT MROs must be licensed physicians with specified knowledge, qualification training, examination, and continuing education. The MRO must not have a prohibited financial relationship with the laboratory and must exercise independent medical judgment. Other programs should define equivalent qualifications appropriate to the consequence of the test.

Review of laboratory information

The MRO checks identifying information, custody documentation, laboratory certification, reported analytes, validity findings, and significant discrepancies. Negative results may receive administrative review, while confirmed nonnegative results normally require donor contact and a verification interview.

The verification interview

The MRO or authorized staff attempts to contact the donor confidentially. At the interview, the MRO explains the reported result, asks about recent medical treatment and prescriptions, and gives the donor an opportunity to present a legitimate medical explanation. The donor may be asked to authorize contact with a treating professional or pharmacy.

Medication details should go to the MRO, not an ordinary supervisor. The MRO evaluates whether documentation is authentic, current, and capable of explaining the specific analyte and concentration.

Legitimate medical explanations

A valid prescription can cause the MRO to verify a laboratory-confirmed result as negative under the governing rules. It does not automatically establish that the employee is safe or medically qualified for every duty. When a medication or condition may create a significant safety risk, limited medical information may be reported only as authorized by the applicable rule.

Results the MRO may verify

Depending on the program, the MRO may report negative, positive for a named drug or metabolite, refusal because of adulteration or substitution, cancelled, invalid, or a result requiring another collection. The MRO applies technical criteria rather than moral judgment and should not expand the panel or disclose unrelated diagnoses.

Split-specimen rights

For an eligible federal result, the MRO informs the donor of the right to request testing of the split specimen and the deadline. The request must be honored even if payment has not been arranged in advance. The second laboratory reports to the MRO, who determines the final effect under the rule.

Confidentiality and reporting

The MRO transmits the verified result to the designated employer representative or other authorized recipient through a secure method. The report generally contains the result and required identifiers—not the donor’s full medical history. Federal rules specify when safety-relevant medical information may be disclosed.

What an MRO does not decide

  • whether an employer must hire or retain someone;
  • whether a person was behaviorally impaired at a particular time;
  • whether a person has a substance-use disorder;
  • whether a nonregulated policy is lawful in a particular state; or
  • whether every prescribed medication is compatible with a safety-sensitive job.

Those questions may require the employer, regulator, treating professional, qualified occupational clinician, or legal counsel.

Sources

Medical and regulatory review: October 29, 2026.