Medical Review Officer (MRO) Explained: What Happens After a Non-Negative THC Test (Screen → Confirm → Report)

Quick answer: An MRO (Medical Review Officer) is typically a licensed physician who reviews certain workplace drug test results to ensure accurate handling under the program’s rules—often after a non-negative screen and/or lab confirmation.

Educational only. Not medical or legal advice. VerdantDetox does not provide instructions for cheating, tampering with, or evading drug tests.

Table of contents

What is an MRO?

An MRO serves as a medical/procedural checkpoint in many workplace testing programs—especially regulated programs. Their role often includes verifying that the testing process followed program rules and reviewing certain results before final reporting.

The typical pathway: screen → confirm → review

While programs differ, a common structure looks like:

  • Initial screen: rapid testing that may report negative or non-negative
  • Confirmation (if required): more specific lab testing (often GC/MS or LC/MS)
  • MRO review/report: administrative and medical review under policy rules

What “non-negative” means

“Non-negative” is often a procedural term indicating the screen requires follow-up (such as confirmation or review). It doesn’t always mean a final positive report on its own—policy dictates next steps.

Split specimens and retesting (high-level)

Some programs collect split specimens so that a retained portion may be tested again under program rules. This is part of why chain-of-custody and documentation matter.

FAQ

Do all employers use MROs?

No. Many non-regulated employers may not use an MRO, while many regulated programs do.

Can an MRO change lab chemistry?

An MRO doesn’t change the lab’s analytical result. They apply program rules and review procedures to determine what is officially reported.

References

Verdant Herbals