Why drug test kits have drug cut-off levels.
What are Drug Cut-off levels?
Drug Cut-off levels are the point at which a test is either a presumed positive or negative. A negative test is when the drug level is below a value set by NIDA. The cut-off varies depending on which drug is in question. For example: looking at the table below, we see that the cut-off level for Amphetamines is 1000 ng/ml. If that drug is detected in a test, then it will be above that value.
The result from an instant test does not tell how much of that drug is detected, it merely indicates ‘presumed positive’ (above 1000 ng/ml). To know how much, we send the sample to a lab for confirmation.
In a test, the result is displayed in panels on the face of the test. In the image below, it shows with two colored lines, one in the (C) area and one in the (T) area. Levels higher than that are considered a presumed positive when only one colored line is visible (C) and NO LINE is visible in the (T) area.
NOTE: Presumed positive test samples should be sent to a SAMHSA approved lab for confirmation. Their results will confirm a positive result if drugs are found above those levels.
Should I use a laboratory if the drug cut-off levels show a presumed positive?
The short answer is YES. Whenever the drug cut-off levels exceed screening levels the test is presumed positive. All positive drug screens should be confirmed by GC/MS (Gas Chromatography/Mass Spectrometry) at a SAMHSA certified laboratory. This is due to the fact that any laboratory or instant rapid drug screens, no matter how accurate, are not 100% accurate in identifying drugs of abuse in urine.
GC/MS confirmation is very specific when looking for drugs and also quantifies the target metabolite with a number in ng/ml. GC/MS confirmations sent to a certified laboratory will also stand up in the court of law if the test result is challenged by a donor.
Screen cut-off levels for rapid urine tests conform to the chart below as per National Institute on Drug Abuse (NIDA) recommendations.
|Drug||Identifier||Drug cut-off||Lab cut-off|
|Amphetamines||(AMP)||1000 ng/ml||500 ng/ml|
|Barbiturates||(BAR)||300 ng/ml||200 ng/ml|
|Buprenorphine||(BUP)||10 ng/m||5 ng/ml|
|Benzodiazepines||(BZO)||300 ng/ml||200 ng/ml|
|Cocaine 150||(COC)||150 ng/ml||150 ng/ml|
|Cocaine||(COC)||300 ng/ml||150 ng/ml|
|Ecstasy||(MDMA)||500 ng/m||250 ng/ml|
|Marijuana||(THC)||50 ng/ml||15 ng/ml|
|Methamphetamine 500||(mAMP)||500 ng/ml||500 ng/ml|
|Methamphetamine||(mAMP)||1000 ng/ml||500 ng/ml|
|Methadone||(MET)||300 ng/ml||200 ng/ml|
|Morphine||(MOP)||300 ng/ml||150 ng/ml|
|Opiates||(OPI)||2000 ng/ml||2000 ng/ml|
|Oxycodone||(OXY)||100 ng/m||300 ng/ml|
|Phencyclidine||(PCP)||25 ng/ml||25 ng/ml|
|Propoxyphene||(PPX)||300 ng/m||200 ng/ml|
|Tricyclic Antidepressants||(TCA)||1000 ng/m||1000 ng/ml|
Note: Do not compare Screen cut-off and Lab GC/MS cut-off levels as the testing methodology is different.
What are detection times?
Detection times are estimates and apply only to urine drug screens. There are many factors that can determine how long a particular drug can be detected in a person, these include; their age, weight, sex, metabolic rate, the amount of drug consumed and over what time frame. No conclusions can be drawn as to when a particular drug was taken or how much was consumed with urine drug screens. If you get a positive from a drug screen we recommend a lab test, which which we can arrange. More specific information can then be obtained with the results from a confirmation test.
|Propoxyphene||6 hours to 2 days|
|Hallucinogens||Lysergic Acid||1-5 days|
|Marijuana and Cannabinoids||Single Use – 2-7 days|
30 to 45 days
|Phencyclidine||Single Use – 1 week|
|Stimulants||Cocaine||Single Use – 3 days|
|Amphetamines||Single Use – 3 days|
|Methylene-2, 4 dioxy-methamphetamine||Single Use – 24 hours|
|Methamphetamine||Single Use – 48 hours|
|Alcohol & Metabolites||Ethanol||Less than 1 day|
|Methanol||Less than 1 day|
|Isopropanol||Less than 1 day|
|Acetone||Less than 1 day|
|Ethylene Glycol||Less than 1 day|
|Benzodiazepines||Diazepam||Single Use – Not detected|
|Oxazepam||Single Use – Not detected|
|Alprazolam||Single Use – Not detected|
|Clonazepam||Single Use – Not detected|
|Chlordiazepoxide||Single Use – Not detected|
|Lorazepam||Single Use – Not detected|
|Ketamine||Less than 72 hours|
What is a Medical Review Officer?
A medical review officer (MRO) is a physician that has been trained and certified to interpret and report drug screen results. If the lab reports a specimen as negative, the MRO signs off on the negative drug screen result. The MRO is responsible for calling a donor who has produced a positive urine specimen after the lab has reported the confirmed positive result. The MRO must ask the donor if there is any reason they can provide to justify the positive drug screen. In the case of marijuana or cocaine there is virtually no justification (except the very rare possibility of marinol, which is a prescription drug containing marijuana that can be prescribed for post chemotherapy nausea or possibly glaucoma). For positives that can result from prescription drugs, the MRO must determine if the donor has a prescription for a drug that would cause the positive drug screen result. If the donor claims to have a prescription for a drug that could have caused the positive result, then the MRO must obtain a copy of the prescription form the doctor or the pharmacy that issued the prescription. If the prescription is deemed to have caused the positive result, then the MRO reports that the drug screen was “Negative”.
Example: If the donor were to claim that they had a methamphetamine positive because they used a Vicks inhaler, 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 specimen contains more than 20% d-methamphetamine, then the donor is to be considered positive for illicit methamphetamine use.
If a donor is positive for opiates and confirmed by GC/MS to contain hydrocodone and the donor’s doctor or pharmacist produces a prescription for codeine, oxycodone or some opiate drug other than hydrocodone, then the MRO must report the drug screen as positive for opiates.
An MRO also serves to redirect the donor’s specimen to a second certified laboratory in the event that the donor challenges the accuracy of the laboratory result. The MRO must then look at the drug test results form the second laboratory and determine if they are consistent with the findings from the first laboratory,
DOT drug screens require that an MRO report all drug screen results including negative results.