The drug cut off concentration level is the defined level of drug or metabolite concentration in the specimen (blood, hair, oral fluid / saliva , urine , sweat ).
Any concentration of drug or metabolite at or above the cut off level leads to “non-negative” result while below leads to a negative result.
The amount of drug / drug metabolite that can be detected by and on-site screen , laboratory screen , or quantitative confirmatory test (GC/MS, LC/MS/MS) depends on factors like dosage, method of use, time, metabolism, sex, metabolism, frequency of use, specimen type, methods of drug testing, and other factors.
Immunoassay (IA) technique is used to initially screen the specimen ( lateral flow immunoassay for on-site devices) while a Gas Chromatography and Mass Spectrometry (GS/MS), or Liquid (LC/MS/MS) test is conducted for confirmatory testing.
The five most commonly abused drugs are Cocaine, Amphetamines, Marijuana, Opiates, and Phencyclidine (PCP), however, these are ” outdated ” relative to current drug abuse patterns in society. Prescription drug misuse is the dominant health and safety concern, in addition to alcohol. PCP using is virtually zero. ” DOT ” testing does not produce “positives” for Oxycontin (Oxycodone ) or Lortab / Vicodine (Hydrocodone).
Urine Drug Testing
In Urine drug testing, the immunoassay (IA) technique is used to perform initial screening of specimen and detect the presence of drugs.
If the concentration of specified drugs is found at or above the cut-off level in initial screening, the results are declared as positive. Later a Gas Chromatography and Mass Spectrometry (GS/MS) test is conducted in laboratory for confirmation.
The initial drug cut off concentration level for five commonly abused drugs using 5-Drug Test Card are:
Cocaine (Benzoylecgonine) — 300 ng/ml
Amphetamines (D-Amphetamine) — 1000 ng/ml
Marijuana (11-nor-?9-THC-9 COOH) — 50 ng/ml
Opiates (Morphine) — 2000 ng/ml
Phencyclidine (Phencyclidine) — 25 ng/ml
The Cut-off levels in urine drug testing are measured in nanograms per milliliter (ng/ml).
The major issues with urine testing is that it is easily and commonly defeated by drug abusers via adulteration and substitution. Also, traditional five panel tests do not detect the prevalent prescription drugs abused.
Hair Drug Testing
The hair drug testing can show drug abuse history for as long as 90 days, however, has can only be performed at a laboratory, and can not detect drug use within the past week or longer… thus only viable for historical drug abuse.
Furthermore, there are issues with variability in results due to hair color.
The initial drug cut off concentration level for the five commonly abused drugs using 7-panel test are:
Cocaine (Benzoylecgonine) — 0.5 ng/mg
Amphetamines (Amphetamine) — 0.5 ng/mg
Marijuana (cannabinoids) — 0.005 ng/mg
Opiates (Morphine) — 0.2 ng/mg
Phencyclidine (Phencyclidine) — 0.3 ng/mg
The confirmatory drug cut-off levels for these drugs are:
Amphetamines (Amphetamine) — 0.1 ng/mg
Marijuana (cannabinoids) — 0.1 ng/mg
Opiates (Morphine) — 0.1 ng/mg
Phencyclidine (Phencyclidine) — 0.1 ng/mg
Oral Fluid / Saliva Drug Testing
Oral fluid is the proper term, as only 20% of substance in the mouth is saliva. Oral fluid drug testing is an effective way to detect the presence of drugs consumed in last few days, thus well suited for most employers that are primarily concerned with recent and/or “on-the-job” misuse. It is also generally concerned superior for post accident or reasonable suspicion testing as it most closely mimics the results obtained from blood testing.
It is convenient, non-invasive, and gives quick results.
The immunoassay technique is used for initial screening of oral specimen for detection of drugs for on-site devices and/or at a laboratory. A GS/MS or LC/MS/MS test is used for confirmatory purpose if initial screening test is non-negative.
The initial cut off concentration for five common drugs in oral drug testing:
Cocaine (Benzoylecgonine) — 20 ng/ml
Amphetamines (d-Amphetamine) — 50 ng/ml
Marijuana (THC-COOH) — 4-50 ng/ml
Opiates (Morphine) — 20 ng/ml
Phencyclidine (Phencyclidine) — 10 ng/ml
The cut-off concentration, drug class detected, and specimen type are crucial parameters to detect the presence of drugs and conclude whether result is non-negative or negative.
As a non-negative and eventually positive test result can have a significant impact on safety in the workplace as well as providing employee assistance.