Under the U.S. Department of Transportation (DOT) mandated and non-mandated substance abuse testing programs, a Medical Review Officer (MRO) is a licensed physician responsible for receiving and reviewing laboratory drug test results and evaluating medical explanations for certain results. The MRO may be assisted by additional non-physician staff such as an MRO Assistant (MROA) who performs certain administrative functions such as receipt and sorting of forms, and provides non-negative and fatally flawed files to the MRO for review.

In order to become a qualified MROA, an individual must have detailed knowledge of their responsibilities and not only thoroughly understand the process itself, but know which specific functions and tasks the MROA can and cannot assist the MRO with. Many organizations and associations in the drug and alcohol testing industry offer convenient and quality MROA training.

• DOT regulations including duties of employers, collection sites, MROs and MROAs
• Receiving and reviewing custody-and-control forms to identify correctible, potentially fatal and fatal flaws requiring the cancellation of drug tests
• Preparing materials for review by MROs for all results that are labeled positive, adulterated, substituted or invalid
• Supporting MROs in contacting individuals to discuss results
• Corroborating and documenting alternative medical explanations for non-negative drug test results
• Serving as liaison with laboratories to secure information and order reanalysis or split specimen analysis
• Communicating with collection sites, laboratories, employer representatives, substance abuse professionals and MROs
• Addressing medical confidentiality and information disclosure issues

It is important to note that under the DOT drug and alcohol testing procedures, the MRO must supervise the MRO assistant. This supervision includes personal oversight of that assistant's work; personal involvement in evaluating, hiring, and firing the assistant, line authority over the assistant for decisions, direction, and control; and regular contact and oversight concerning drug testing program matters. The MRO's supervision and control cannot be superseded by or delegated to anyone else with respect to test result review and other functions performed by the MRO assistant.