Testing for drugs


                This topic has been debated for over a decade. Analytical methods have advanced, and the drug test pool has expanded from mainly amphetamines to include most drugs of abuse. With this in mind, it is time to review the DOT 5 panel drug testing requirements for common substances that may result in a positive drug screen, but do not generally fit within the category of “non-negative”. A urine specimen will be considered non-negative if any one or more of these five drugs are detected at a concentration equal to or greater than 0.02 ng/ml:

                Amphetamines (Dextroamphetamine, Levamfetamine) Note: Methamphetamines metabolite was removed from testing in 2010

                Cocaine (Benzoylecgonine)

                Marijuana Metabolite (THC Carboxylic Acid)

                Phencyclidine (PCP, angel dust)

                Opiates (Morphine, Codeine, 6-Monacteyl Morphine) [opiate metabolites]

Urine samples that screen negative for drugs in the five drug classes above will be reported as such. A positive test result will then be followed by a confirmation test to identify any substance(s), other than the five listed above, that may have caused a positive initial screen. The confirmation cutoff concentration is generally either 500 ng/ml or 2,000 ng/ml of each substance tested. A confirmation test result that exceeds the cutoff concentration will be reported as positive.

  Please note that marijuana metabolites are not included in this list. It is very common for DOT drug screen results to report a non-negative status, even if THC Carboxylic Acid is present at significant concentrations, due to the very low cutoff concentration of 15 ng/ml.

The following substances will not generally cause a non-negative drug screen under the parameters listed above:

                Alcohol (Methanol) NOTE: If an alcohol screen does not dilute properly , reasonable suspicion should exist to request testing via an alternative specimen collection method AND follow agency policy regarding possible adulteration or substitution of specimen.


NOTE: Some agencies use breathalyzers for alcohol testing. These breathalyzer analyzers will only detect the presence of alcohol, not other adulterating or substituting substances.

                All Lysergic Acid Diethylamide (LSD) metabolites

                Anabolic Steroids

*Please note that this list is a sampling and not all inclusive. It cannot be emphasized enough that each laboratory has its own unique testing menu and complete analysis of the specimen must take place in accordance with the respective laboratory’s procedures. In addition, because of inherent limitations in immunoassay technology , it may be that a non-negative status will occur from one drug class while another drug class does not cause a non-negative result. The combination of both drugs can result in a non-negative status.

Please note on the SAMHSA Mandatory Guidelines for Federal Workplace Drug Testing Programs, Appendix B. “Federal Register” Vol. 69 No 20 , pages 52874 – 52889 , 2004 that if any of these five drug classes are detected below the cutoff level but at a concentration equal to or greater than 2 times the cutoff level, those results must be reported as positive and a confirmation test must be performed: amphetamines (Dextroamphetamine, Levamfetamine), cocaine metabolite, opiates metabolites, PCP and marijuana metabolite. If any of these substances are detected at a concentration less than twice the cutoff levels listed above but equal to or greater than 1 ½ times the cutoff concentration, those results must also be reported as positive. Finally, if any of these substances are detected at a concentration less than 1 ½ times the cutoff, but greater than twice the cutoff concentration, follow agency policy regarding possible adulteration or substitution of specimen.

Please note that this is not an all inclusive list of drugs that may cause non-negative DOT drug screen results. This information should only serve to provide insight into the basic process of drug testing in order for laboratories to better service their customers with reference materials and quality service when requested for clarification on their drug testing menu or possible misfiled specimens.

Marijuana metabolite (THC Carboxylic Acid) is included in the “five most abused” controlled substance classes which do not generally cause a non-negative drug screen under the parameters listed above.

NOTE: Not all cutoff levels can be verified online, so when in doubt please contact the respective laboratory for the cutoff level you are inquiring about. Any inquires regarding possible adulteration or substitution of specimen must be reported to your Medical Review Officer (MRO) and to your agency’s security office IMMEDIATELY .

*As we said before these lists are not complete and may vary from one testing lab to another. For example: GHB is not considered a “five most abused” substance by SAMHSA and will often show up as part of GCMS panel if requested, but it does not interfere with drug testing results. We hope you find this list helpful.


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