Marijuana and the Cannabinoids

158 Tsai
immunoassay test to eliminate negative urine specimens from further consideration
and to identify the presumptively positive specimens that require confirmation or further
testing.” The guidelines mandate that the initial test “shall use an immunoassay
which meets the requirements of the Food and Drug Administration (FDA) for commercial
distribution.” The guidelines also permit multiple initial tests (or rescreening)
to be performed utilizing different immunoassays for the same drug or drug class
under the stipulation that “all tests meet all Guideline cutoffs and quality control
requirements.”
The regulated approach to initial screening “permits rapid identification of presumptive
positives within a framework of extensive quality control and offers a defined
reference if the next step confirmation is required.” This allows a process with a set
“administrative cutoff” for uniform comparison across different assay principles and
various volumes of screening. The specified cutoff levels for cannabinoids testing were
set at 100 ng/mL for immunoassays and 15 ng/mL for GC/MS in the first Mandatory
Guidelines (53 FR 11970, 1988). The cutoff for immunoassay was lowered to 50 ng/mL
in the subsequent version of the federal guidelines (91). In case a retest is required for
a specimen or for the testing of Bottle B of a split specimen, the federal guidelines state
that the retest quantification is not subject to a cutoff requirement. However, the retest
“must provide data sufficient to confirm the presence of the drug or metabolite” (90).
The proposed revisions for the next version of the Mandatory Guidelines (91,92)
will include regulations on specimen validity testing, POCT, and alternative specimen
testing. Additionally, the new guidelines will expand the authorized confirmation
method from only GC/MS to allow the use of additional confirmation technologies
such as LC/MS. However, the new guidelines draft does not change the cutoff requirements
for cannabinoid testing. Other civilian drug-testing programs, such as the College
of American Pathologists Forensic Urine Drug Testing laboratory accreditation
program, allow the cutoff determinations be made according to the need of the laboratory
or to the intent of its clients’ drug-testing programs. Generally speaking, even in
nonregulated sectors, many drug-testing programs follow the cutoff defined by the federal
guidelines and require reporting positive results if both the initial immunoassay
results and the GC/MS analysis are at or above their respective cutoff concentration.
The provisions of the rules that affect US corporations may be imposed on their
global employees. In contrast, countries in the European Union, Asia, and Australia
differ in their concerns and strategies in relation to substance abuse problems. Surveys
of DAT in European Union laboratories in the late 1990s indicated that a high percentage
of laboratories did not use or report cutoff (93–95). A few work groups in Europe
have proposed consensus or country-specific guidelines and cutoffs, including drugtesting
application-specific cutoffs, for DAT (see, e.g., refs. 96–98). The European
Laboratory Guidelines for Legally Defensible Workplace Drug Testing were developed
by the European Workplace Drug Testing Society with an aim to “establish best
practice” for laboratories within Europe “whilst allowing individual countries to operate
within the requirements of national customs and legislation” (98). For urine drug
testing, the maximum cutoff for screening test and the confirmation cutoff recommended
by the European Workplace Drug Testing Society for cannabis metabolites
are the same as those mandated by the current SAMHSA guidelines.