The drug cut off concentration level is the defined level of drug or metabolite concentration in the specimen. Any concentration of drug or metabolite at or above the cut off level leads to positive result while below leads to a negative result. The amount of drugs that can be detected by labs depends on factors like drug detection time, metabolism, frequency of use, specimen type, methods of drug testing, and other factors. Immunoassay (IA) technique is used to initially screen the specimen while a Gas Chromatography and Mass Spectrometry (GS/MS) test is conducted for confirmation. The five most commonly abused drugs are Cocaine, Amphetamines, Marijuana, Opiates, and Phencyclidine (PCP).

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).

Hair Drug Testing
The hair drug testing is more accurate than any other method of drug testing. It can show drug abuse history for as long as 90 days. For hair drug testing, Enzyme Immunoassay (EIA) technique is used for initial screening. If the results are found positive, a GS/MS test is conducted for confirmation. Accurate results are provided as hair drug testing is performed in laboratories under controlled environments. 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

Saliva Drug Testing
The saliva drug testing is an effective way to detect the presence of drugs consumed in last few hours. It is convenient, non-invasive, and gives quick results. The concentration of detectable drugs in saliva is less compared to urine testing. The immunoassay technique is used for initial screening of saliva specimen for detection of drugs. A GS/MS test is used for confirmatory purpose if initial screening test is positive. The initial cut off concentration for five common drugs in saliva drug testing using 6 panels oral fluids devise are:
Cocaine (Benzoylecgonine)                    – 20 ng/ml
Amphetamines (d-Amphetamine)           – 50 ng/ml
Marijuana (THC-COOH)             – 12 ng/ml
Opiates (Morphine)                                – 40 ng/ml
Phencyclidine (Phencyclidine)         – 10 ng/ml

The cut-off concentration is a crucial parameter to detect the presence of drugs and conclude whether result is positive or negative. As a positive test result can have a significant impact on person, various advanced techniques like GS/MS are used to accurately determine the concentration of drugs in specimen, confirm the result, and rule out false positive results.

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