Jacob Bell
New Member
On September 1, 1994, the US
Department of Health and Human
Services (DHHS) requirement for the
immunoassay screening cutoff concentration
of marijuana metabolite
was decreased from 100 to 50 pgfL (1 ).
Numerous studies have compared the
effectiveness of various immunoassay
reagents at 50 and 100 p.g/L cutoff
values on clinical or controlled specimens
(2-9). Here we use historical
data to determine the effect of the
above reduction on the increased percentage
of workplace specimens that
will screen positive for cannabinoids,
the increased percentage of specimens
that will be confirmed as positive for
1 1-nor-A-9-tetrahydrocannabinol-9-
carboxylic acid (THCA) by gas chromatography-
mass spectrometry
(GC-MS), and the effectiveness of the
drug detection program.
Specimens (n =30402) from unregulated
commercial clients were screened
on an Olympus AU5131 analyzer with
the Roche Abuscreen Online Cannabinoid
Assay (Roche Diagnostics Systems,
Branchburg, NJ) at a cutoff of 50
1ıigfL. The resulting positives (n = 401)
were rescreened at 100 ıgfL with the
Emit II Cannabinoid Assay (Syva Co.,
San Jose, CA). Because of laboratory
changes, the kits were from two different
manufacturers; however, the Syva
and Roche kits have similar performance
characteristics when used at the
50 pg/L cutoff (9). When the 401 specimens
were rescreened at the 100 pg/L
cutoff with the Emit II Cannabinoid Assay,
only 286 specimens were positive;
that is, reducing the screening cutoff to
50 ıtgfL increased the number of specimens
that screened positive for cannabinoids
by 40.2%.
The 401 specimens that screened
positive at the 50 ıig/L cutoff were analyzed
by GC-MS with selective ion
monitoring (4); 383 were confirmed to
contain >15 ıigfL THCA (the DHHS
confirmation cutoff for THCA by GCMS).
Of the 286 specimens that
screened positive at 100 ıg/L, all were
confirmed positive by GC-MS (>15
p.gIL THCA). For the 115 specimens
that screened positive at 50 ı&gIL but
negative at the 100 ıig/L cutoff, 97
were confirmed positive by GC-MS
(>15 pgfL THCA), 16 were not confirmed,
and 2 contained THCA at <15
ızgfL. The 14 unconfirmed specimens
may be due to adulterants or other
substances in the urine that cross-react
in the 50 ıagIL cutoff assay. Overall,
therefore, the increase in positive
samples upon changing from 100 to 50
ıgfL cutoff was 9 7/286 = 33.9%.
Table 1 shows the distribution of
GC-MS specimen concentrations in relation
to the two screening cutoff values.
Of the 383 specimens that confirmed
positive (15 pg/L THCA),
CLINICAL CHEMISTRY, Vol. 40, No. 11, 1994 2115
92% had THCA concentrations 30
ızgfL. Of the 97 specimens that
screened negative at 100 pgfL, 80%
had quantitative values for THCA of
30 pıgfL. This suggests that reducing
the screening cutoff to 50 pgIL will not
result in laboratories being flooded
with large numbers of specimens for
which the THCA concentrations are
within 20% of the 15 ıig/L confirmation
cutoff.
The THCA-positive detection rate
for the 30402 specimens analyzed at
the 100 p.g/L cutoff was 0.94%. This
rate was increased to 1.26% by lowering
the cutoff to 50 ıg'L. We conclude
that the effectiveness of drug detection
programs will be enhanced by reducing
the screening cutoff for cannabinoids.
The cost-effectiveness of a company's
drug testing program is often
determined by calculating the cost per
positive test. However, the true expense
of drug testing is based on the
cost of collection, transportation, laboratory
analyses, and Medical Review
Officer services. The additional specimens
screened positive will result in
an increased laboratory cost for the
additional confirmations, but the
other costs involved in drug testing
will remain the same. Therefore, the
cost-effectiveness of a company's drug
testing program based on the cost per
positive specimen will actually decrease
because of the increased detection
rate for cannabinoid use. Any increase
in cost due to additional
confirmations will be offset by economic
savings to employers because of
financial liabilities associated with
the employment of drug users.
References
1. Mandatory guidelines for federal workplace
drug testing programs. Fed Beg 1994;
59:29908-31.
2. Irving J, Leeb B, Foltz RL, Cook CE,
Bursey JT, Willette RE. Evaluation of immunoassay
for cannabinoids in urine. J
Anal Toxicol 1984;8: 192-fl.
3. Jones AB, ElSohly HN, Arafat ES, El-
Sohly MA. Analysis of the major metabolite
of delta-9-tetrahydrocannabinol in
urine. W. A comparison of five methods. J
Anal Toxicol 1984;8:249-51.
4. Baker TS, Harry JV, Russell JW, Myers
RL. Rapid method for the GC/MS confirmation
of 11-nor-9-carboxy-ı9-tetrahydrocannabinol
in urine. J Anal Toxicol 1984;8:
255-9.
5. Fredrick DL, Green J, Fowler MW.
Comparison of six cannabunoids metabolite
assays. J Anal Toxicol 1985;8:116-20.
6. Paul BD, Mell LD Jr, Mitchell JM,
McKinley RM, Irving J. Detection and
quantitation of urinary 1 1-nor-delta-9-tetrahydrocannabinol-
9-carboxylic acid, a metabolite
of tetrahydrocannabinol, by capillary
gas chromatography and electron impact
impact
mass fragmentography. J Anal
Toxicol 1987;11:1-5.
7. Funkle BS, Black D, Blanke RV, Butler
TJ, Jones GR, Sample RHB. Analysis for
commonly abused drugs in urine at selected
threshold ("cutoff") concentrations
[Letter]. Cliii Chem 1991;37:586-7.
8. ElSohly MA, Jones AB, ElSohly HN,
Cross-reactivity of selected compounds in
the Abbott TDX cannabinoid assay. J Anal
Toxicol 1990;14:277-9.
9. Huestis MA, Mitchell JM, Cone EJ. Lowering
the federally mandated cannabinoid
uxununoassay cutoff increases true-positive
results. Cliii Chem 1994;40:729-33.
Barbara J. Rowland1'3
John Irving1
Elizabeth S. Keith2
1RocJı Biomed. Labs.
Southaven, MS 38671
2Dept. of Biol.
Memphis State Univ.
Memphis, TN
Source: Increased detection of marijuana use with a 50 micrograms/L urine screening cutoff
Department of Health and Human
Services (DHHS) requirement for the
immunoassay screening cutoff concentration
of marijuana metabolite
was decreased from 100 to 50 pgfL (1 ).
Numerous studies have compared the
effectiveness of various immunoassay
reagents at 50 and 100 p.g/L cutoff
values on clinical or controlled specimens
(2-9). Here we use historical
data to determine the effect of the
above reduction on the increased percentage
of workplace specimens that
will screen positive for cannabinoids,
the increased percentage of specimens
that will be confirmed as positive for
1 1-nor-A-9-tetrahydrocannabinol-9-
carboxylic acid (THCA) by gas chromatography-
mass spectrometry
(GC-MS), and the effectiveness of the
drug detection program.
Specimens (n =30402) from unregulated
commercial clients were screened
on an Olympus AU5131 analyzer with
the Roche Abuscreen Online Cannabinoid
Assay (Roche Diagnostics Systems,
Branchburg, NJ) at a cutoff of 50
1ıigfL. The resulting positives (n = 401)
were rescreened at 100 ıgfL with the
Emit II Cannabinoid Assay (Syva Co.,
San Jose, CA). Because of laboratory
changes, the kits were from two different
manufacturers; however, the Syva
and Roche kits have similar performance
characteristics when used at the
50 pg/L cutoff (9). When the 401 specimens
were rescreened at the 100 pg/L
cutoff with the Emit II Cannabinoid Assay,
only 286 specimens were positive;
that is, reducing the screening cutoff to
50 ıtgfL increased the number of specimens
that screened positive for cannabinoids
by 40.2%.
The 401 specimens that screened
positive at the 50 ıig/L cutoff were analyzed
by GC-MS with selective ion
monitoring (4); 383 were confirmed to
contain >15 ıigfL THCA (the DHHS
confirmation cutoff for THCA by GCMS).
Of the 286 specimens that
screened positive at 100 ıg/L, all were
confirmed positive by GC-MS (>15
p.gIL THCA). For the 115 specimens
that screened positive at 50 ı&gIL but
negative at the 100 ıig/L cutoff, 97
were confirmed positive by GC-MS
(>15 pgfL THCA), 16 were not confirmed,
and 2 contained THCA at <15
ızgfL. The 14 unconfirmed specimens
may be due to adulterants or other
substances in the urine that cross-react
in the 50 ıagIL cutoff assay. Overall,
therefore, the increase in positive
samples upon changing from 100 to 50
ıgfL cutoff was 9 7/286 = 33.9%.
Table 1 shows the distribution of
GC-MS specimen concentrations in relation
to the two screening cutoff values.
Of the 383 specimens that confirmed
positive (15 pg/L THCA),
CLINICAL CHEMISTRY, Vol. 40, No. 11, 1994 2115
92% had THCA concentrations 30
ızgfL. Of the 97 specimens that
screened negative at 100 pgfL, 80%
had quantitative values for THCA of
30 pıgfL. This suggests that reducing
the screening cutoff to 50 pgIL will not
result in laboratories being flooded
with large numbers of specimens for
which the THCA concentrations are
within 20% of the 15 ıig/L confirmation
cutoff.
The THCA-positive detection rate
for the 30402 specimens analyzed at
the 100 p.g/L cutoff was 0.94%. This
rate was increased to 1.26% by lowering
the cutoff to 50 ıg'L. We conclude
that the effectiveness of drug detection
programs will be enhanced by reducing
the screening cutoff for cannabinoids.
The cost-effectiveness of a company's
drug testing program is often
determined by calculating the cost per
positive test. However, the true expense
of drug testing is based on the
cost of collection, transportation, laboratory
analyses, and Medical Review
Officer services. The additional specimens
screened positive will result in
an increased laboratory cost for the
additional confirmations, but the
other costs involved in drug testing
will remain the same. Therefore, the
cost-effectiveness of a company's drug
testing program based on the cost per
positive specimen will actually decrease
because of the increased detection
rate for cannabinoid use. Any increase
in cost due to additional
confirmations will be offset by economic
savings to employers because of
financial liabilities associated with
the employment of drug users.
References
1. Mandatory guidelines for federal workplace
drug testing programs. Fed Beg 1994;
59:29908-31.
2. Irving J, Leeb B, Foltz RL, Cook CE,
Bursey JT, Willette RE. Evaluation of immunoassay
for cannabinoids in urine. J
Anal Toxicol 1984;8: 192-fl.
3. Jones AB, ElSohly HN, Arafat ES, El-
Sohly MA. Analysis of the major metabolite
of delta-9-tetrahydrocannabinol in
urine. W. A comparison of five methods. J
Anal Toxicol 1984;8:249-51.
4. Baker TS, Harry JV, Russell JW, Myers
RL. Rapid method for the GC/MS confirmation
of 11-nor-9-carboxy-ı9-tetrahydrocannabinol
in urine. J Anal Toxicol 1984;8:
255-9.
5. Fredrick DL, Green J, Fowler MW.
Comparison of six cannabunoids metabolite
assays. J Anal Toxicol 1985;8:116-20.
6. Paul BD, Mell LD Jr, Mitchell JM,
McKinley RM, Irving J. Detection and
quantitation of urinary 1 1-nor-delta-9-tetrahydrocannabinol-
9-carboxylic acid, a metabolite
of tetrahydrocannabinol, by capillary
gas chromatography and electron impact
impact
mass fragmentography. J Anal
Toxicol 1987;11:1-5.
7. Funkle BS, Black D, Blanke RV, Butler
TJ, Jones GR, Sample RHB. Analysis for
commonly abused drugs in urine at selected
threshold ("cutoff") concentrations
[Letter]. Cliii Chem 1991;37:586-7.
8. ElSohly MA, Jones AB, ElSohly HN,
Cross-reactivity of selected compounds in
the Abbott TDX cannabinoid assay. J Anal
Toxicol 1990;14:277-9.
9. Huestis MA, Mitchell JM, Cone EJ. Lowering
the federally mandated cannabinoid
uxununoassay cutoff increases true-positive
results. Cliii Chem 1994;40:729-33.
Barbara J. Rowland1'3
John Irving1
Elizabeth S. Keith2
1RocJı Biomed. Labs.
Southaven, MS 38671
2Dept. of Biol.
Memphis State Univ.
Memphis, TN
Source: Increased detection of marijuana use with a 50 micrograms/L urine screening cutoff
