A presumptive positive is a screening result at or above a laboratory's cutoff concentration. It is not a final result, not a diagnosis, and not proof that a person used a drug without a prescription. Under the federal rule that governs cutoff concentrations for laboratory drug tests, a result at or above the initial test cutoff simply triggers a confirmation test on the same specimen. Only after that confirmation test, and in most workplace programs a review by a medical review officer, does a result become verified negative or verified positive. This article explains what happens between the screen and the verified result, the cutoff numbers involved, the confirmation methods labs use, how a documented prescription changes the outcome, and what employers may and may not do while a result is still pending.
Presumptive Positive Means Non Negative, Not Confirmed
Most immunoassay screening tests, including the cups and dip cards used in workplace and point of collection testing, report a result as negative or non negative rather than positive or negative. A non negative screen, sometimes called presumptive positive or preliminary positive, means the specimen produced a signal at or above the cutoff concentration for one or more drug classes. The federal cutoff rule for laboratory based urine testing states it directly: on an initial test, a laboratory must report a result below the cutoff as negative, and if the result is at or above the cutoff it must conduct a confirmation test, then report that confirmation result as negative or confirmed positive depending on where it falls against the confirmatory cutoff, which is often lower than the screening cutoff and always analyte specific under 49 CFR 40.85. In plain terms, a presumptive positive is a flag that says test this specimen further, not a finished answer.
Immunoassay screens are built for speed and sensitivity, not specificity. Structurally similar compounds, including some over the counter medications and prescription drugs, can cross react with the antibodies in a screening assay and push a negative specimen over the cutoff. That is the entire reason the federal framework requires a second, different analytical method before anyone calls a result positive. The regulatory definition of a confirmatory drug test describes exactly that second look: a second analytical procedure performed on a different aliquot of the original specimen to identify and quantify a specific drug or drug metabolite, as defined in 49 CFR 40.3.
Confirmation Testing: Gas Chromatography Mass Spectrometry and LC-MS/MS
Laboratories certified for federal workplace testing confirm a non negative screen using gas chromatography mass spectrometry (GC-MS) or liquid chromatography tandem mass spectrometry (LC-MS/MS). These methods separate and identify molecules by mass and structure rather than by antibody binding, which is why they are far less prone to the cross reactivity that produces a screening false positive. The Substance Abuse and Mental Health Services Administration (SAMHSA), the agency within HHS that sets the scientific and technical requirements for federal drug free workplace programs, describes this two tier screen and confirm structure on its workplace programs page, and the current cutoff concentrations trace back to the HHS Mandatory Guidelines rulemaking published in the Federal Register. A specimen only reaches this confirmatory step because the initial screen came back non negative. A specimen that screens negative is never sent for GC-MS or LC-MS/MS confirmation because there is nothing to confirm; see SAMHSA's workplace programs overview for how the federal program structures that testing chain.
Common Screening and Confirmation Cutoffs
The table below reflects the federal cutoff concentrations for laboratory based urine drug testing used in DOT regulated and other federal workplace programs, expressed in nanograms per milliliter (ng/mL), as codified at 49 CFR 40.85. Non-DOT and private employer programs may set their own panels and cutoffs, and state law and employer policy vary, so a specific workplace program should always be checked against its own written cutoff table.
| Drug or Drug Class | Initial Screening Cutoff | Confirmatory Test Cutoff |
|---|---|---|
| Marijuana metabolite (THCA) | 50 ng/mL | 15 ng/mL |
| Cocaine metabolite (benzoylecgonine) | 150 ng/mL | 100 ng/mL |
| Codeine and morphine | 2000 ng/mL | 2000 ng/mL |
| Hydrocodone and hydromorphone | 300 ng/mL | 100 ng/mL |
| Oxycodone and oxymorphone | 100 ng/mL | 100 ng/mL |
| 6 acetylmorphine (heroin marker) | 10 ng/mL | 10 ng/mL |
| Phencyclidine (PCP) | 25 ng/mL | 25 ng/mL |
| Amphetamine and methamphetamine | 500 ng/mL | 250 ng/mL |
| MDMA and MDA | 500 ng/mL | 250 ng/mL |
Oral fluid testing runs on a separate cutoff table with its own initial and confirmatory concentrations under 49 CFR 40.91, which is why an oral fluid non negative and a urine non negative are not directly comparable even for the same drug class.
The Medical Review Officer Interview
In DOT regulated and many non-DOT workplace programs, a laboratory confirmed non negative result does not go straight to the employer. It goes to a medical review officer (MRO), a licensed physician trained to review drug testing results, act as an independent gatekeeper for the accuracy of the process, and determine whether there is a legitimate medical explanation for the result before it is ever verified and released, per 49 CFR 40.123. The MRO reviews the chain of custody paperwork, then conducts a verification interview that includes direct contact with the employee in person or by telephone, as required under 49 CFR 40.129. Only after that interview, or after documented attempts to reach the employee under narrow exceptions in the rule, may the MRO verify the result as negative, cancelled, or positive.
This interview is where a legitimate prescription can change the outcome. For marijuana, cocaine, amphetamines, semi synthetic opioids such as hydrocodone and oxycodone, and PCP, the MRO must verify a confirmed non negative result as positive unless the employee presents a legitimate medical explanation, which can include a legally valid prescription consistent with the Controlled Substances Act. The employee carries the burden of presenting that documentation at the interview, and the regulation is explicit that the MRO may not second guess whether the prescribing clinician should have written the prescription, only whether the explanation is legitimate, under 49 CFR 40.137. In practice this means an employee flagged for a non negative opioid result who has a current, verifiable prescription in their own name for a legitimately prescribed medication may see that result verified negative once the MRO confirms the documentation, while an employee who cannot produce a legitimate explanation for the same result is verified positive.
What Employers May and May Not Do While a Result Is Pending
A presumptive or non negative screen is not, by itself, grounds for an adverse employment decision under the federal testing framework. DOT regulated employers are generally prohibited from standing an employee down, meaning removing them from safety sensitive duties, before the MRO completes verification, unless the employer holds a specific waiver from the relevant DOT agency for that purpose, under 49 CFR 40.21. That waiver process is narrow, requires documented safety justification, and is granted by the DOT agency, not the employer. Employers who are not covered by DOT testing rules set their own policies, and state law on what an employer may do with a pending or non negative result varies, so any written policy should be checked against the specific state and DOT status of the workforce rather than assumed. What an employer may generally not do, regardless of program, is treat a presumptive positive as equivalent to a confirmed, verified positive result, or take permanent action based on a screen alone before the confirmation and MRO process has run its course.
What a Verified Result Looks Like
Once the MRO completes the verification interview and any needed follow up, the result is reported to the employer in one of three ways: verified negative, cancelled, or verified positive, along with refusal to test findings for adulterated or substituted specimens. A cancelled test is treated as though it did not occur for most purposes and typically triggers a recollection. A verified positive means the laboratory confirmation and the MRO review both support the finding, and the legitimate medical explanation process has been offered and not established. Only a verified result, not the original screen, is the basis for the personnel actions and reporting duties that follow a workplace testing program.
None of this process is designed to be defeated. Employees and applicants should never attempt to interfere with specimen collection or validity testing, and doing so is treated under the same regulations as a refusal to test. The purpose of the screen, confirm, and MRO sequence is accuracy, not an opportunity to avoid detection.
For a closer look at how long the confirmation and reporting steps typically take once a specimen leaves the collection site, see our post on how long lab confirmation results take after a non negative screen. For what happens on the employer side after a result is verified, see what happens if you fail a pre-employment drug test. Employers building or reviewing a screening program can browse CLIA waived cups and dip cards designed around these federal cutoff concentrations in our drug test cup collection.
Frequently asked questions
Is a presumptive positive the same as a positive drug test?
No. A presumptive positive, also called a non negative or preliminary positive, is a screening result at or above the initial cutoff concentration. It becomes a positive only after a confirmation test using a different analytical method, and in most workplace programs after a medical review officer verifies the result.
Why does a screen need to be confirmed at all?
Immunoassay screening tests are sensitive but not perfectly specific, so structurally similar compounds can occasionally cross react and produce a non negative result for a substance that is not actually present. Confirmation testing by GC-MS or LC-MS/MS identifies and quantifies the specific drug or metabolite on a different aliquot of the same specimen.
Can a prescription change a presumptive positive result?
Yes, for several drug classes. If a laboratory confirms a non negative result for marijuana, cocaine, amphetamines, semi synthetic opioids, or PCP, the medical review officer must offer the employee a chance to present a legitimate medical explanation, which can include a legally valid prescription, before verifying the result as positive.
Can an employer remove someone from duty just because of a presumptive positive?
DOT regulated employers are generally prohibited from standing an employee down before the MRO completes verification unless they hold a specific DOT waiver. Non-DOT employer practices and state law vary, so a pending non negative result should not be treated the same as a verified positive result.
What confirmation cutoff applies if the screening cutoff is different?
Confirmatory cutoffs are set separately from screening cutoffs and are often lower for the same drug class. For example, the federal urine cutoff for marijuana metabolite is 50 ng/mL on the initial screen and 15 ng/mL on confirmation, while other analytes such as codeine and morphine use the same cutoff at both stages.
Does a presumptive positive mean the same thing on an oral fluid test as a urine test?
No. Oral fluid tests use their own separate table of initial and confirmatory cutoff concentrations, so a non negative oral fluid screen is not directly comparable to a non negative urine screen for the same drug class.
This article is general information for employers and is not legal or medical advice. Testing programs should confirm current cutoff concentrations, panel design, and verification procedures with their laboratory, medical review officer, and legal counsel.
