By HealthDataConsortium.org Research Team
A non-negative drug screen is often not the last step. In federally regulated urine testing, a screening result at or above the cutoff is followed by a separate laboratory confirmation test, and a Medical Review Officer (MRO) reviews laboratory results from the testing program. This article maps those stages and lists questions to ask about the program that applies to you. Other programs can work differently, so it stays at the level the cited sources support.
The Short Answer
Under the U.S. Department of Transportation (DOT) rules for urine testing, the laboratory reports a screening result below the cutoff as negative. A result at or above the cutoff triggers a confirmation test. A confirmation result below its cutoff is reported as negative, and one at or above it is reported as confirmed positive. DOT describes the MRO as the licensed physician who receives and reviews laboratory results and evaluates medical explanations for certain results. Your employer's or clinic's program may follow different rules, so ask which ones apply to you.
Process Map: How Result Verification Works Under DOT Rules
This map covers verification of a laboratory result only. It does not explain how to read result labels such as dilute or invalid, which are separate topics. The stages follow the DOT sources listed at the end.
- Initial (screening) test. The laboratory runs a first test on the urine specimen. A result below the initial cutoff is reported as negative. A result at or above the cutoff moves to confirmation.
- Confirmation test. A second laboratory test is run on a result that met or exceeded the initial cutoff. Below the confirmation cutoff, the result is reported as negative. At or above it, the result is reported as confirmed positive.
- Medical Review Officer review. The MRO is a licensed physician who receives and reviews laboratory results generated by an employer's testing program. DOT describes the MRO as an independent and impartial gatekeeper for the accuracy and integrity of the testing process. The MRO determines whether there is a legitimate medical explanation for laboratory-confirmed positive, adulterated, substituted and invalid results.
- Reporting and confidentiality. DOT lists timely flow of results and other information to employers, and protection of the confidentiality of testing information, among the MRO's responsibilities.
- Further procedures. DOT's MRO page points to other parts of the federal rule for split specimen tests (Subpart H) and problems in drug tests (Subpart I). What is available to you, and when, depends on the rule in force for your program.
What the Federal Cutoffs Say for THC
DOT's urine cutoff rule lists marijuana metabolites (THCA) at 50 ng/mL for the initial test and 15 ng/mL for the confirmation test. The rule adds that when a laboratory uses an alternate technology for the initial THCA test, it must use the same 15 ng/mL cutoff for both tests. These figures come from the DOT rule as published on its site, which shows a last-updated date of June 6, 2023. They apply to DOT-regulated urine testing. An employer's non-DOT program, an oral fluid test or a clinical screen may use other numbers, so ask for the ones that apply to you.
Questions to Ask About Your Program
- Is this test covered by DOT rules, or is it an employer policy or clinical screen? DOT publishes an Am I Covered? page for this purpose.
- What are the screening and confirmation cutoffs, and what specimen type is being tested?
- Will a confirmation test be run before any result is reported to the employer or care team?
- Who is the MRO or reviewing clinician, and how will I be contacted?
- Is a split specimen or second test available, and what is the deadline to request one?
- Who receives the result, and what is kept confidential?
Limits of This Article
- It describes DOT's federal process. Non-DOT workplace, legal, school and clinical programs set their own rules, and this article does not cover them.
- It does not interpret dilute, invalid, adulterated or substituted result labels.
- It does not estimate how long THC remains detectable, and it gives no guidance on timing tests, driving or avoiding a positive result.
- It is not medical or legal advice. HealthDataConsortium.org is an independent publication, not a medical practice or government agency, and does not employ physicians or licensed practitioners. See the site's Medical Disclaimer and Editorial Standards.
Who Should Get Professional Advice
Anyone facing a confirmed positive, a dispute about a result, or a job or licence consequence should talk to the program's MRO or a qualified employment or health attorney. Someone who uses cannabis for a medical reason, or who is unsure whether a prescription or product could affect a result, should raise it with the reviewing clinician and their own healthcare provider.
What to Do Next
- Ask the program administrator for the written testing policy and the review procedure.
- If you may be DOT-covered, DOT lists employee resources and Part 40 Questions and Answers on its site.
- For related background on this site, see Types of Drug Tests for THC, Cannabis Is Legal in Your State But You Still Have to Pass a Drug Test and CBD and Drug Tests: Can Cannabidiol Cause a False Positive?
Sources
- U.S. Department of Transportation, Office of Drug and Alcohol Policy and Compliance: ODAPC home page
- U.S. Department of Transportation, ODAPC: Medical Review Officers
- U.S. Department of Transportation, ODAPC: 49 CFR §40.85, cutoff concentrations for urine drug tests
