What are Drug Cut-Off Levels, and Why Are They Needed?
In drug testing, a cut-off level refers to the minimum amount or concentration of a drug or its metabolites that must be present in a biological sample, such as urine, blood, or saliva, to trigger a positive result.
Drug testing typically involves screening for a specific drug or a class of drugs using various analytical methods, such as immunoassays, chromatography, or mass spectrometry. The cut-off level is usually determined based on the sensitivity and specificity of the testing method. It is set to minimize the risk of false positive or false negative results.
For example, in the case of a urine drug test for marijuana, the cut-off level for the THC metabolite is typically set at 50 ng/mL. This means that if the concentration of THC metabolites in the urine sample is below this level, the test result will be negative, and if it is above this level, the test result will be positive.
It is important to note that the cut-off level can vary depending on the drug, the type of sample being tested, and the testing method used. Employers, sports organizations, and law enforcement agencies may have different cut-off levels depending on their policies and requirements.
Why have a cut-off level?
A cut-off level is used in drug testing to minimize the risk of false positive or false negative results, which could lead to inaccurate conclusions about an individual’s drug use. False positives occur when a drug test result is positive even though the individual did not use drugs. In contrast, false negatives occur when a drug test result is negative even though the individual did use drugs.
Setting a cut-off level helps to ensure that the drug test is sensitive enough to detect drug use when it has occurred while also being specific enough to avoid false positive results due to incidental exposure to drugs or other factors that could interfere with the testing process.
Moreover, cut-off levels provide a standardized and consistent approach to drug testing, which ensures fairness and objectivity when drug testing is required, such as in the workplace, sports, or the criminal justice system.
Overall, cut-off levels are an important aspect of drug testing that helps to ensure the accuracy and reliability of the results and to maintain the integrity and effectiveness of drug testing programs.
Why do we use Drug Cut-Off levels?
Cut-off levels are the minimum concentration or amount of a drug or its metabolites that must be present in a biological sample, such as urine, blood, or saliva, to trigger a positive result in a drug test.
Cut-off levels are used in drug testing for several reasons, including:
- To minimize the risk of false-positive results: False-positive results occur when a drug test indicates the presence of a drug or its metabolites in a sample when, in fact, the individual has not used the drug. By setting an appropriate cut-off level, drug tests can be designed to detect only the presence of a drug or its metabolites above a certain threshold, thereby reducing the likelihood of false positives due to incidental exposure to drugs or other factors that may interfere with the testing process.
- To ensure the test’s sensitivity and specificity: A test’s sensitivity refers to its ability to detect the presence of a drug or its metabolites in a sample, while the specificity of a test refers to its ability to identify negative samples correctly. Drug tests can be designed to balance sensitivity and specificity by setting appropriate cut-off levels, maximizing their accuracy and reliability.
- To standardize testing procedures: Cut-off levels provide a consistent and standardized approach to drug testing, ensuring that testing procedures are applied consistently and fairly across different individuals and settings.
Overall, cut-off levels are an important component of drug testing that helps to ensure the accuracy and reliability of the results while also reducing the risk of false positives and other sources of error.
Results from an assay are displayed in panels on the face of the device. In the images below, each assay shows colored lines or bars, one in the (C) and one in the (T) areas. A presumed positive is when only one colored line is visible (C) with no apparent line in the (T) area.
The images above tell us the result of a drug screen under different scenarios. In Fig 1., the image shows the results are NEGATIVE as all lines/bars are visible. In Fig 2., this is a PRESUMED POSITIVE when no (T) line or bar is visible. This example applies to Cocaine and Opiates; The metabolite of Cocaine was detected at a level higher than 300 ng/mL, and the metabolite for Opiates was over 2000 ng/mL. Anything higher than these levels is presumed positive. Confirm your presumed sample utilizing Gas Chromatography-Mass Spectrometry at a SAMHSA-approved lab. Fig 3. is the result of an INVALID analysis, generally due to insufficient sample volume.
Urine Cut-Off Levels
Drug Name | Code | Detection Time | Cut-Off level |
---|---|---|---|
Amphetamines | AMP | 2-4 Days | 1000 ng/mL |
Barbiturates | BAR | 4-7 Days | 300 ng/mL |
Benzodiazepines | BZO | 3-7 Days | 300 ng/mL |
Buprenorphine | BUP | 1-3 Days | 10 ng/mL |
Cocaine | COC | 2-4 Days | 300 ng/mL |
Ecstasy | MDMA | 1-3 Days | 500 ng/mL |
EtG Alcohol | EtG | Up to 80 Hours | 300 ng/mL |
Fentanyl | FTL | 1-3 Days | 200 ng/mL |
Marijuana | THC | 2-30 Days | 50 ng/mL |
Methadone | MTD | 3-5 Days | 300 ng/mL |
Methamphetamine | mAMP | 3-5 Days | 1000 ng/mL |
Morphine | MOR | 2-4 Days | 300 ng/mL |
Opiates | OPI | 2-4 Days | 2000 ng/mL |
Oxycodone | OXY | 2-4 Days | 100 ng/mL |
Phencyclidine | PCP | 7-14 Days | 25 ng/mL |
Propoxyphene | PPX | 1-2 Days | 300 ng/mL |
Synthetic Marijuana | K2/Spice | 2-10 Days | 50 ng/mL |
Tricyclic Antidepressants | TCA | 7-10 Days | 1000 ng/mL |
Saliva Cut-Off Levels
Drug Name | Code | Detection Time | Cut-Off Level |
---|---|---|---|
Alcohol | ALC | 6-12 Hours | >0.02% B.A.C. |
Amphetamines | AMP | 1-3 Days | 50 ng/mL |
Barbiturates | BAR | 1-4 Days | 60 ng/ml |
Benzodiazepines | BZO | 1-3 Days | 50 ng/ml |
Buprenorphine | BUP | 1-3 Days | 5 ng/mL |
Cocaine | COC | 1-3 Days | 20 ng/mL |
Ecstasy | MDMA | 1-3 Days | 50 ng/mL |
Fentanyl | FTL | 1-3 Days | 10 ng/mL |
Marijuana | THC | 6-12 Hours | 25 ng/mL |
Methadone | MTD | 1-3 Days | 75 ng/ml |
Methamphetamine | mAMP | 1-3 Days | 50 ng/mL |
Opiates | OPI | 1-3 Days | 40 ng/mL |
Oxycodone | OXY | 2-3 Days | 50 ng/mL |
Phencyclidine | PCP | 1-3 Days | 10 ng/mL |
Propoxyphene | PPX | 1-3 Days | 50 ng/mL |
Tramadol | TRA | 1-2 Days | 50 ng/mL |
Tricyclic Antidepressants | TCA | 1-2 Days | 50 ng/mL |
Should I use a laboratory if the result is positive?
A laboratory should always be used to confirm a presumed positive urine sample. Whenever you get a presumed positive, it is impossible to know how much is in their system and if the rapid test worked correctly. A laboratory will test your sample and confirm your suspicions with Gas Chromatography-Mass Spectrometry (GC-MS); This is the preferred method for testing and will quantitate the amount found reported in ng/mL. Always use a SAMHSA-certified laboratory for testing.
GC/MS confirmation is unequivocal when looking for drugs and quantifies the target metabolite with a number. If a donor challenges the test result, a GC/MS confirmation from a certified laboratory will stand up in a court of law.
All FDA-cleared drug screening test results adhere to strict cut-off levels, as shown in the charts below.
Source: National Institute on Drug Abuse (NIDA).
Can I proclaim my innocence if the drug cut-off levels show I’m positive?
When a donor gets a positive test result for opioids after being confirmed by GC-MS testing, it may be because it contains hydrocodone, which is a prescription drug. If the donor can’t produce a prescription for this, then the MRO must report the result as positive for opioids. Conversely, if they can provide an order that satisfies the MRO, the test with be reported as negative.
If the donor were to claim that they used a Vicks inhaler and were positive for methamphetamine, then the MRO would order a d/l isomer separation to determine if the drug present in the specimen is at least 80% l-methamphetamine. If the sample contains more than 20% d-methamphetamine, then the donor should be considered positive for illicit methamphetamine use.
An MRO also redirects the donor’s specimen to a second certified laboratory if the donor challenges the laboratory result’s accuracy. The MRO must then look at the drug test results from the second laboratory and determine if they are consistent with the findings from the first laboratory,
DOT or Federal drug tests require that an MRO report all drug results, positive or negative.
What are Drug detection times?
Drug detection times refer to the period during which a drug or its metabolites can be detected in a biological sample following drug use, such as urine, blood, or saliva. The detection time can vary depending on several factors, including the drug itself, the dosage and frequency of use, the individual’s metabolism, and the tested sample type.
Some drugs can be detected for a few hours or days after use, while others can be detected for weeks or even months. Here are some general detection times for commonly tested drugs:
- Amphetamines: 1-3 days
- Cocaine: 1-3 days
- Marijuana: 1-30 days (depending on the frequency of use and potency)
- Opiates: 1-3 days (short-acting), up to a week (long-acting)
- Benzodiazepines: 1-3 days (short-acting), up to a week (long-acting)
- PCP: 1-8 days
It’s important to note that detection times are not the same as the drug’s half-life, which is the time it takes to metabolize and eliminate the drug from the body. Detection times can vary based on several factors, as mentioned above, and can also be affected by the sensitivity and specificity of the testing method.
Drug detection times are important in drug testing because they help determine the appropriate window of time for testing following drug use. However, it’s worth noting that drug tests cannot determine whether an individual was under the influence of a drug at the time of testing, as they only detect the presence of drugs or their metabolites in the body.
A full list of abused substances and urine and oral fluid detection times can be found here.
Why are Medical Review Officers used when determining a drug test result?
Medical Review Officers (MROs) are used when determining a drug test result because they play a critical role in ensuring the accuracy and integrity of the drug testing process. MROs are licensed physicians trained and certified to review and interpret drug test results and handle any potential medical or legal issues arising from the testing process.
MROs have several key responsibilities, including:
- Reviewing drug test results: MROs review the results of drug tests to determine if they are positive or negative and to verify that the testing was conducted correctly and in compliance with established protocols.
- Confirming positive test results: If a drug test is positive, the MRO will contact the individual to confirm any prescription medications or other legitimate reasons for the positive result. The MRO may also request additional testing to confirm the presence of the drug or metabolite in question.
- Ensuring confidentiality and privacy: MROs are responsible for protecting the privacy and confidentiality of individuals tested for drugs. They are trained in HIPAA regulations and other laws governing the handling of medical information.
- Handling legal and medical issues: MROs may be involved in resolving any legal or medical issues that arise from drug testing, such as providing expert testimony in legal cases or making recommendations for treatment or rehabilitation.
Overall, MROs play a critical role in ensuring the accuracy and integrity of the drug testing process and protecting the rights and privacy of individuals tested for drugs. Their expertise and training are essential for maintaining the reliability and effectiveness of drug testing programs in various settings, including the workplace, sports organizations, and the criminal justice system.
We conclude that drug cut-off levels are essential to determine if a donor is presumed positive or negative. They are used as the reference or marker for determining if the result of a test is over or under the legal limit as dictated by SAMHSA.