What Does 10DSP/No THC/PHN Mean on a Drug Test?

The notation “10DSP/No THC/PHN” describes a specific configuration of a workplace or pre-employment urine drug test. “10DSP” stands for 10-Drug Screen Panel, meaning the lab tests for ten categories of controlled substances. “No THC” means the panel has been modified to exclude tetrahydrocannabinol, the active compound in marijuana. “PHN” refers to phencyclidine, the dissociative drug commonly known as PCP, confirming it remains on the panel. You will typically see this kind of shorthand on a lab order, a requisition form, or an employer’s testing policy, and understanding it helps you know exactly what the test is and is not looking for.

What a 10-Drug Screen Panel Covers

A standard 10-panel drug screen tests urine for ten substance categories. The exact lineup can vary slightly between labs, but the most common version tests for amphetamines, methamphetamine, barbiturates, benzodiazepines, cocaine, marijuana (THC), methadone, opiates, phencyclidine (PCP), and propoxyphene. Some panels swap propoxyphene for another substance like oxycodone or MDMA (ecstasy), depending on the employer’s requirements. The U.S. Department of Health and Human Services has published mandatory guidelines for federal workplace drug testing that originally focused on five substance classes and later proposed expansions covering MDMA and related compounds.¹

When you see “10DSP” on your paperwork, it simply means the employer or ordering provider selected the ten-substance version rather than a smaller five-panel or seven-panel screen. A ten-panel test is common in healthcare, government-adjacent, and safety-sensitive positions where a broader net is considered appropriate. The specific drugs included depend on the lab and the employer, so the “No THC” and “PHN” notations clarify which substances are in and which are out for your particular test.

Why THC Gets Excluded From Some Panels

The “No THC” modifier is increasingly common and reflects a shift in how employers handle marijuana testing. As more states have legalized recreational or medical cannabis, many employers have opted to remove THC from their standard drug panels. Some state laws now prohibit employers from testing for marijuana at all, or from using a positive THC result as grounds for adverse action. Even in states without such laws, companies in competitive labor markets have dropped THC testing because it can shrink their applicant pool without meaningfully improving workplace safety.

From a testing standpoint, removing THC simply means the lab skips the immunoassay for cannabinoid metabolites. The rest of the panel stays intact. If your test order says “No THC,” a positive result for marijuana metabolites will not be reported even if they happen to be present in your sample, because the lab is not looking for them. This does not mean you have blanket permission to use cannabis freely at work. Employers may still have policies prohibiting impairment on the job, and some industries regulated at the federal level, like commercial transportation, continue to mandate THC testing regardless of state law.

What the PHN Designation Means

PHN is a lab abbreviation for phencyclidine, better known as PCP or “angel dust.” Its presence on the panel notation confirms that phencyclidine screening is included in your test. This is worth knowing because phencyclidine testing has a well-documented history of producing false positive results. Common prescription medications can cross-react with the immunoassay antibodies designed to detect PCP, triggering a positive result in someone who has never used the drug. A case report documented exactly this scenario in a patient taking prescribed medication who tested positive for PCP on an initial urine immunoassay, with the false result only being resolved through more specific confirmatory analysis.²

If you are taking any prescription or over-the-counter medications, this matters. A false positive for PCP can carry serious consequences for employment, legal proceedings, or clinical decision-making. The standard safeguard is confirmatory testing, which uses a different, more specific technology to verify or rule out the initial screening result. Knowing that PHN is on your panel gives you a reason to disclose your medications proactively, either to the collection site or to the Medical Review Officer who evaluates positive results.

How the Initial Screen Works

The first pass on any drug panel uses an immunoassay, a test that relies on antibodies designed to bind to specific drug molecules or their metabolites. When a metabolite is present in the urine above a set threshold (called the cutoff level), the antibody reaction produces a measurable signal and the result is flagged as “presumptive positive.” Every substance on the panel has its own cutoff. For federal workplace testing, the Substance Abuse and Mental Health Services Administration (SAMHSA) sets these thresholds. Different specimen types use different cutoffs, and these values have been evaluated and debated extensively across testing programs.³

Immunoassays are fast and relatively inexpensive, which is why they serve as the first step. But they are not perfect. The antibodies can bind to molecules that are structurally similar to the target drug, producing false positives. A review of the literature identified 25 reports of false positive results caused by commonly prescribed medications, including antihistamines, antidepressants, antibiotics, pain relievers, antipsychotics, and over-the-counter drugs like ibuprofen, naproxen, and diphenhydramine. False positives for amphetamine and methamphetamine were the most frequently reported.⁴ More recently, solriamfetol (a medication for excessive daytime sleepiness) and a major metabolite of trazodone have both been shown to trigger false positive amphetamine results on certain immunoassay platforms.⁵

A negative result on immunoassay is typically reported as final. A presumptive positive, however, triggers a second round of testing.

Confirmatory Testing and Why It Matters

When a screening immunoassay comes back positive, the same sample is sent for confirmatory analysis using a more precise technology, most commonly liquid chromatography-mass spectrometry (LC-MS) or gas chromatography-mass spectrometry (GC-MS). These methods physically separate the molecules in the sample and identify them by their unique mass signatures, which eliminates the cross-reactivity problem that plagues immunoassays.⁶

This two-step process is a core principle of regulated drug testing. A result is not considered a confirmed positive until it has passed both the screening and confirmatory stages. If the confirmatory test does not find the suspected substance, the original positive is overturned. This is why a single immunoassay result should never be treated as definitive, whether in a workplace, clinical, or legal setting. If you receive a positive screening result and believe it is a false positive, the confirmatory step is your built-in safety net.

The Medical Review Officer’s Role

Even after confirmatory testing, a positive result does not automatically go to your employer as-is. In regulated programs, a physician called a Medical Review Officer (MRO) reviews every confirmed positive. The MRO contacts you to determine whether there is a legitimate medical explanation for the result, such as a valid prescription for a medication that would cause the positive.⁷

This step makes a substantial practical difference. In a large workplace drug testing study, the majority of confirmed positive results for opiates, amphetamines, and benzodiazepines turned out to have legitimate medical explanations once an MRO reviewed them. Roughly seven in ten opiate positives, six in ten amphetamine positives, and four in ten benzodiazepine positives were verified by an MRO as being due to medical prescriptions. Cannabis and cocaine positives, by contrast, were almost entirely attributed to illicit use.⁸

The takeaway is that a confirmed positive is not necessarily the end of the road. If you have a prescription for a benzodiazepine, an opioid pain medication, or a stimulant like Adderall, the MRO can downgrade the result so it is not reported as a failed test. You will need to provide documentation, usually a pharmacy record or a prescriber’s confirmation. Having your prescriptions organized before you go in for a drug test saves time and anxiety during this process.

Specimen Validity Testing

Alongside the drug panel itself, the lab also checks whether your urine sample is genuine and unaltered. This is called specimen validity testing, and it looks at several markers. Labs measure creatinine concentration to determine whether the sample is too dilute, either from excessive water intake or deliberate adulteration. If the creatinine is below a certain threshold, the lab may also check the specific gravity of the sample using a refractometer.⁹ The pH of the sample is also measured, and some labs test for the presence of oxidizing or reducing chemicals that could be used to destroy drug metabolites.¹⁰

If your sample falls outside normal parameters for any of these checks, it may be reported as “dilute,” “substituted,” or “invalid” rather than negative. A dilute result often means you will be asked to retest. A substituted or invalid result can be treated the same as a refusal to test under some employer policies. The simplest way to avoid a dilute result is not to overhydrate in the hours before your test. Drinking a normal amount of water is fine; chugging several liters is likely to push your creatinine below the acceptable threshold.

Detection Windows Are Less Predictable Than You Think

One of the most common questions people have around drug testing is “how long does substance X stay in my system?” The honest answer is that it varies enormously. Detection times depend on the dose, the route of administration, individual metabolism, body composition, whether someone used a substance once or regularly, the pH of the urine, and the sensitivity of the particular assay being used.¹¹¹²

As a rough guide, most stimulants like amphetamines and cocaine metabolites are detectable in urine for a few days after use. Opiates have a similar window. Benzodiazepines vary widely depending on whether the specific drug is short-acting or long-acting; some can be detected for weeks. Phencyclidine, the PHN on your panel, typically has a detection window of several days for occasional use but can linger longer in chronic users. These ranges are approximations, and the charts you find online are generalizations that may not apply to your specific situation. Two people who take the same dose of the same drug on the same day can test positive for different lengths of time.

What Standard Panels Do Not Catch

A 10-panel screen, even a modified one, only looks for what it is designed to look for. Substances that are not on the panel will not be detected, and newer synthetic drugs often fall outside the scope of standard immunoassays entirely. A case report illustrated this limitation when a patient presented with symptoms consistent with gamma-hydroxybutyrate (GHB) overdose, but the standard hospital drug screen returned negative for GHB because it simply was not part of the panel. The patient’s urine did test positive for methamphetamine, but the substance causing the most acute danger was invisible to the standard screen.¹³

This gap is worth understanding because it cuts both ways. If you are an employer relying on a 10-panel screen to catch all substance use, you should know that synthetic cannabinoids, novel stimulants, and club drugs like GHB and ketamine are not on most standard panels. If you are taking the test, you should know that substances not listed on your panel are simply not being tested. The notation on your lab order, like “10DSP/No THC/PHN,” is a transparent list of what is and is not included. Read it carefully, and if anything is unclear, the ordering provider or the collection site can tell you the full list of substances on your specific panel.

Urine Versus Oral Fluid Testing

Urine remains the most common specimen type for workplace drug testing, but oral fluid (saliva) testing has been gaining ground. The two methods have different strengths. Oral fluid is harder to adulterate because the sample is collected under direct observation. It also tends to detect very recent use better than urine. However, a comparison of workplace urine and oral fluid testing found that urine detected substances in a much larger percentage of samples. In that study, substances turned up in about one in 27 urine samples but only about one in 200 oral fluid samples. Nearly all of the positive cases were caught by urine alone, with only a single worker testing positive on oral fluid but not urine.¹⁴

The federal guidelines have proposed allowing oral fluid testing alongside urine for federal workplace programs. For now, urine is still the default for most regulated testing. If your order says “10DSP,” it almost certainly means a urine test unless stated otherwise. Oral fluid testing is more commonly used in post-accident or reasonable-suspicion testing where speed and tamper resistance matter more than a long detection window.

A Positive Drug Test Does Not Measure Impairment

One persistent misconception about drug testing is that a positive result means the person is currently impaired. Urine drug tests detect metabolites, the breakdown products left behind after the body processes a substance. These metabolites can linger in the body long after the psychoactive effects have worn off. A person can test positive for a substance days after last using it, at a point when they are completely unimpaired. Research on cannabis specifically found that levels of THC and related compounds in blood, urine, and oral fluid did not correlate with cognitive or psychomotor impairment for either smoked or vaporized cannabis.¹⁵

This distinction matters because it shapes what a drug test can and cannot tell an employer or a court. A positive urine result is evidence of past exposure to a substance within its detection window. It is not evidence that the person was impaired at the time the sample was collected, or at any particular moment before it. For substances still on your panel, like the nine remaining after THC is removed, the same principle applies. A positive for a benzodiazepine means the metabolite was present, not that you were sedated at work. The MRO review process and the employer’s own policies determine what happens next, but the test itself is a biomarker, not a breathalyzer.

Point-of-Care Tests and Rapid Screening Devices

Some employers and clinics use point-of-care or “rapid” drug test devices rather than sending samples to a central lab. These are the cup-based or dip-card tests that produce results in minutes at the collection site. They use the same immunoassay principle as lab-based screens, and their accuracy is generally good. A comparison study found that on-site urine devices achieved accuracies of 93 to 99 percent for amphetamines, 97 to 99 percent for cannabinoids, 94 to 98 percent for opiates, and 90 to 98 percent for benzodiazepines.¹⁶

Those numbers sound reassuring, but even a 93 percent accuracy rate means roughly seven out of every hundred results could be wrong. In a high-volume testing program, that adds up to a meaningful number of incorrect results. Rapid tests are useful for immediate screening, but any positive result from a point-of-care device should still be confirmed by laboratory analysis. Some employers treat a rapid-test positive as grounds for immediate action, like removing someone from a safety-sensitive role pending lab confirmation. If you test positive on a rapid device, ask whether the sample is being sent for confirmation. If it is not, you have grounds to request it.