Printer Friendly

Urinary cannabinoid disposition in occasional and frequent smokers: is THC-glucuronide in sequential urine samples a marker of recent use in frequent smokers?

Cannabis was consumed by 129-230 million 15-64-year-olds in 2011(1). [[DELTA]sup.9]-tetrahydrocannabinol (THC) [3] and its ll-nor-9-carboxy-THC (THCCOOH) metabolite's urinary disposition are well characterized (2-13), although less is known about frequent cannabis smoking and phase II cannabis metabolites. Recent research documented extended excretion of cannabinoids in abstinent chronic daily smokers' blood and urine given THC's lipophilicity and large body stores (8-9, 14-15). THC was detected in 1 cannabis smoker's hydrolyzed urine for 24 days; 11 -hydroxy-THC (11-OH-THC) and THCCOOH were detected for at least 24 days (9).

Accurately identifying recent cannabis intake is important for documenting potential impaired driving, accident causation, sports doping, and relapse during drug abuse treatment. Researchers have proposed models to identify new use in occasional (10) and frequent cannabis smokers (11) on the basis of total THCCOOH concentrations and time between 2 samples. Although these proposed models identified new use between 2 urine samples >24 h (occasional smokers' model) or >48 h apart (chronic frequent smokers' model), to our knowledge there is no model to accurately identify recent use from samples collected shortly after smoking, during the intoxication and impairment period. THC [greater than or equal to] 1.5 [micro]g/L in occasional smokers' urine (following enzymatic hydrolysis) (4) and THC-glucuronide [greater than or equal to] 2.3 [micro]g/L (equivalent to 1.5 [micro]g/L THC) (16) were suggested as markers of recent cannabis intake. To our knowledge, cannabidiol (CBD) and cannabinol (CBN) in urine have not yet been studied as recent use markers.

Phase II cannabinoid metabolite disposition has not been fully elucidated. Cannabinoids are mainly glucuronidated, with possible minor sulfation (17). Studies documenting urinary THCCOOH and THCCOOH-glucuronide disposition used workplace (18), random cannabis abstainers' (19) or stability samples (20), or they compared THCCOOH before and after hydrolysis (13, 21-22). Unconjugated THC and 11-OH-THC are not detected or detected in low concentrations (11-OH-THC only) in urine and require enzymatic or tandem enzymatic-alkaline hydrolysis to cleave glucuronides (19,23-24). However, given the inability to definitively ensure complete hydrolysis, direct glucuronide analysis provides more accurate information regarding urinary metabolite disposition.

Here we simultaneously determined THC, 11-OH-THC, THCCOOH, CBD, CBN, THC-glucuronide, and THCCOOH-glucuronide concentrations in 14 frequent and 10 occasional smokers' urine following a single smoked 6.8% THC cigarette. We monitored cannabinoid phase I and II urinary metabolites for 30 h by liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Materials and Methods

PARTICIPANTS

Healthy male and female study participants provided written informed consent to participate in this National Institute on Drug Abuse Intramural Research Program Institutional Review Board-approved study. Individuals were recruited by advertisements, flyers, and participant referrals. Participants were medically and psychologically evaluated to verify compliance with inclusion criteria: 18-45 years old; self-reported mean frequency of cannabis smoking of <2X/week (occasional smoker) or [greater than or equal to] 4X/week (frequent smoker) in the past 3 months; and a positive urine cannabinoid test for frequent smokers. Exclusion criteria included breastfeeding or pregnant, current medical condition or history of neurological illness, clinically significant adverse events associated with cannabis intoxication, >450 mL blood donation within 30 days of drug administration, clinically significant anemia; increased blood pressure or heart rate >100 bpm after 5-min rest, clinically significant electrocardiogram abnormality, or interest in drug abuse treatment, currently or within 60 days of study screening. Pregnancy tests were administered at screening and on study admission to women with reproductive potential.

STUDY DESIGN

Participants entered the secure research unit approximately 19 h before smoking to preclude intoxication at cannabis dosing. Participants smoked 1 [mean (SD)] 6.8% (0.2%) (54 mg) THC, 0.25% (0.08%) CBD, and 0.21% (0.02%) CBN cannabis cigarette ad libitum within 10 min. All urine was collected ad libitum from admission to 30 h after cannabis smoking into 250-mL polypropylene bottles (Thomas Scientific) and immediately refrigerated for <12 h. After volume determination, urine was aliquoted into 3.6-mL polypropylene Nunc cryotubes (Thomas Scientific), frozen, and analyzed within 24 h, except repeat analyses and dilutions completed within 48 h.

URINE CANNABINOID ANALYSIS

Urine samples were analyzed for THC, 11-OH-THC, THCCOOH, CBD, CBN, THC-glucuronide, and THCCOOH-glucuronide by LC-MS/MS according to a previously published method (25). Linear ranges were 2-100 [micro]g/L for THC and CBN, 1-100 [micro]g/L for 11-OH-THC and CBD, 1-250 [micro]g/L for THCCOOH, 0.5-50 [micro]g/L for THC-glucuronide, and 5-500 [micro]g/L for THCCOOH-glucuronide [lowest number is limit of quantification (LOQ)]. Interassay (n = 50) analytical bias and imprecision were 92.2%-102.2% and 5.2%-10.2%, respectively. Urine creatinine was measured on a Roche/Hitachi Modular D2400 analyzer by colorimetric assay based on the Jaffe reaction.

DATA ANALYSIS

Total cannabinoids excreted over time were calculated by multiplying cannabinoid concentration by urine void volume and adding analyte mass. Total THCCOOH (equivalent to unconjugated THCCOOH and THCCOOH-glucuronide) was calculated by adding molar THCCOOH and THCCOOH-glucuronide masses converted to THCCOOH concentrations. Creatinine-normalized concentrations were calculated by dividing cannabinoid concentration by creatinine concentration, providing concentrations in micrograms cannabinoid per gram creatinine ([micro]g/g). Several cutoffs were evaluated to determine adequate cutoffs for markers of recent use: 1,2, and 5 [micro]g/L and 2 and 5 [micro]/g for THCCOOH; 0.5, 1, 2, and 5 [micro]g/L and 2 and 5 [micro]g/g for THC-glucuronide; and 5 [micro]g/L for THCCOOH-glucuronide. Total THCCOOH was evaluated at the 15-[micro]g/L cutoff set by the US Department of Health and Human Services (26) and at the 175-[micro]g/L decision limit recently announced (May 11,2013) by the World Anti-Doping Agency (27). Pharmacokinetic parameters and group differences were compared by use of the Mann-Whitney exact test. Group differences in positive cannabinoid test frequency were evaluated by use of the [chi square] test. All analyses were done with SPSS Version 20, with 2-tailed P < 0.05 considered significant. In recent use prediction models, true-positive (TP) (new use and new use predicted), true-negative (TN) (no new use and new use not predicted), false-positive (FP) (no new use but new use predicted), and false-negative (FN) (new use but new use not predicted) results were calculated, and diagnostic sensitivity, specificity, and efficiency were determined.

Results

HUMAN PARTICIPANTS

Fourteen healthy and frequent and 10 healthy and occasional smokers (17 males, 7 females), ages 19-41 years, participated. Demographics are described in Table 1 of the Data Supplement that accompanies the online version of this report at http://www.clinchem.org/content/vol60/issue2.

URINE ANALYSIS

There were 414 urine voids between admission and 30 h after smoking; 412 were collected (participant B missed one predose urine void and participant H missed the first urine void postdose), and of these, 286 were collected postsmoking. Free THC, 11-OH-THC, CBD, and CBN were not detected.

There was a significant association between cannabis use group and positive urine cannabinoid test frequency in the 30 h after smoking ([chi square], 80.6, 170.2, 17.4, and 17.4 for THCCOOH, THC-glucuronide, THCCOOH-glucuronide, and total THCCOOH, respectively, all P values < 0.001). Frequent smokers' odds of having a positive cannabinoid urine test in the 30 h after smoking were 13.0, 107.1, 22.1, and 22.1 times higher than for occasional smokers for these analytes, respectively.

Creatinine-normalized and nonnormalized THC-glucuronide concentrations peaked 0.6-7.4 h after smoking (Table 1 and Fig. 1); THCCOOH and THCCOOH-glucuronide concentrations were highly variable (Table 1; also see online Supplemental Figs. 1 and 2). Maximal concentrations (non- and creatinine normalized) were significantly higher in frequent smokers for THCCOOH, THC-glucuronide, and THCCOOH-glucuronide (Table 2); participant H was excluded from THC-glucuronide comparison because the first urine void following smoking (likely time of maximal concentration) was not collected. Nonnormalized THCCOOH and THCCOOH-glucuronide concentrations displayed high intra- and intersubject variability among frequent smokers. Creatininenormalization did not improve intrasubject variability, except for THCCOOH-glucuronide in frequent smokers, and only then slightly reduced maximal concentration group differences, which remained significantly different (Table 2).

TIME OF LAST POSITIVE

The time of the last positive urine sample was determined for normalized and nonnormalized THCCOOH and THC-glucuronide in occasional smokers at various cutoffs but could not be determined in frequent smokers because of extended cannabinoid excretion (Table 3). The last positive sample frequently occurred after the first negative sample, similar to other studies (5, 8-9), given urinary cannabinoid excretion variability (Fig. 1; also see online Supplemental Figs. 1 and 2). Some participants had up to 6 negative samples between 2 THCCOOH-positivc or THC-glucuronide-positive samples.

DETECTION RATES

The nonnormalized urine positivity rate (6-h time windows) was evaluated at each analyte's LOQ and for total THCCOOH at various cutoffs, including the LOQ and 15 and 175 [micro]g/L (Fig. 2). At a 175-[micro]g/L cutoff, none of the occasional smokers' urine samples were positive, even immediately after smoking; only 50% and 3.9% of frequent smokers' urine samples were positive 0-6 h and 24-30 h after smoking, respectively.

DRUG MASS EXCRETED

Frequent smokers excreted significantly more total cannabinoid mass (moles) than occasional smokers due to previously self-administered cannabis (see online Supplemental Table 2). Because occasional smokers had low or negative cannabinoid concentrations at admission, we calculated the %THC (molar percentage) in the cigarette excreted as each cannabinoid; 0.00032% (0%-0.0[O.sub.4]8%), 0.0037% (0.000024%-0.010%), 0.094% (0.011%-0.323%), and 0.096% (0.011%-0.33%) of THC moles present in the cannabis cigarette were excreted as THCCOOH, THC-glucuronide, THCCOOH-glucuronide, and total THCCOOH, respectively, in urine over 30 h postsmoking.

NEW AND RECENT CANNABIS USE PREDICTION MODELS

THCCOOH/THCCOOH-glucuronide and THC-glucuronide/THCCOOH-glucuronide ratios were calculated, but these values were not effective as markers of recent cannabis smoking owing to high intra- and intersubject variability (see online Supplemental Fig. 3).

[FIGURE 1 OMITTED]

Because the model for chronic daily cannabis smokers (II) requires that samples be collected >48 h apart, we could not evaluate it with our data set. The occasional smoker model has 2 algorithms: one with all samples used for modeling, and the other omitting samples collected in the first 24 h after smoking. Although developed for occasional smokers, these models were never tested with urinary THCCOOH from frequent smokers. With algorithm 1 (at the 95% limit and a 15-[micro]g/L total THCCOOH cutoff), 2222 urine pairs were evaluated. Diagnostic sensitivity, specificity, and efficiency were 29.1%, 93.9%, and 65.8% for frequent smokers and 100%, 91.4%, and 92.7%, for occasional smokers, respectively. With algorithm 2 (excluding samples collected within 24 h of self-reported or controlled smoking), frequent smokers were not evaluated because all but participants F and G smoked the previous day, providing too few true positives for adequate method evaluation. In occasional smokers, 21 paired-positive urine samples had a diagnostic sensitivity, specificity, and efficiency of 100%.

These models require that urine samples be collected before and after new cannabis use, as would occur in routine urine monitoring in drug treatment, parole, or workplace settings. The models cannot be used to identify recent smoking in samples collected shortly after smoking, as would be the case when documenting impaired driving, new use in residential treatment facilities, or accident investigations and for incompetition prohibited drugs in sports. Therefore, we evaluated THC-glucuronide increases immediately after smoking and creatinine-normalized THC-glucuronide in consecutive urine samples as a marker of recent use. All 14 frequent smokers and 10 occasional smokers were included in initial exploratory analysis for markers of recent use to evaluate multiple criteria (Table 4). Frequent smokers had 153 urine pairs [median (range) of 10 (6-19) pairs per participant], of which 144 pairs [9.5 (6-17) pairs per participant] were THC-glucuronide-positive pairs and were included for model development. Therefore, all frequent smokers provided data for the THC-glucuronide recent-smoking criteria. Occasional smokers had 109 pairs [9.5 (4-16) pairs per participant], only 13 of which [0.5 (0-5) pairs per participant] contributed to model development; only 5 occasional smokers had 2 consecutive positive THC-glucuronide samples. All THC-glucuronide-positive samples were collected after smoking and within 8.3 h of each other. An absolute %difference of [greater than or equal to] 50% between 2 consecutive samples and a creatinine-normalized concentration [greater than or equal to] 2 [micro]g/g in the first of the consecutive samples indicates recent use within 6 h of first sample collection with the best diagnostic sensitivity and efficiency.

Discussion

To our knowledge, these are the first urinary THC, 11-OH-THC, THCCOOH, CBD, CBN, THC-glucuronide, and THCCOOH-glucuronide concentration data following controlled cannabis smoking in frequent and occasional smokers with simultaneous direct analysis by LC-MS/MS. Only THCCOOH, THC-glucuronide, and THCCOOH-glucuronide were detected. 11-OH-THC, CBD, and CBN could be present as glucuronide or sulfate conjugates, but commercial conjugated standards are unavailable and thus could not be monitored in our method. Tandem enzymatic-alkaline hydrolysis increased unconjugated 11-OH-THC and CBD concentrations (19, 23, 28); however, quantification following hydrolysis is not as precise as direct analytic measurement, given possible hydrolysis variability.

Frequent smokers were 85.7% African-American, whereas occasional smokers were 30.0% African-American. To our knowledge, there are no studies examining racial differences in cannabinoid metabolism and disposition. THC is metabolized to 11-OH-THC through CYP2C9 (29). Compared to African-Americans, white Americans have higher frequencies of CYP2C9*2 and CYP2C9*3 variant alleles, which exhibit decreased activity compared to the wild-type CYP2C9* 1 (30). Therefore, racial differences in CYP2C9 alleles could potentially confound the observed difference in smoker groups. However, previous research extensively documents extended excretion of cannabinoids in frequent smokers; therefore, we believe that the higher urinary cannabinoid concentrations in frequent smokers are caused by their greater previous cannabis exposure. Male percentages were similar between groups (71% and 70% in frequent and occasional smokers, respectively). Previous research documented no differences between male and female cannabis smokers (31). We are not aware of any studies that have examined the effects of age on cannabinoid metabolism. Although occasional smokers were significantly older (median age 33.0 years) than frequent smokers (median age 24.8 years), we do not believe that this age difference would result in clinically significant differences in cannabinoid metabolism and excretion.

THCCOOH AND THCCOOH-GLUCURONIDE

Nonnormalized THCCOOH and THCCOOH-glucuronide concentrations exhibited large intra- and intersubject variability; only THCCOOH-glucuronide variability was reduced with creatinine normalization (see online Supplemental Figs, land 2). We hypothesize that at lower concentrations, such as those of THCCOOH, minor analyte concentration fluctuations represent a larger overall percentage of the concentration; thus, overall variability might not be compensated for by creatinine normalization. However, differences in renal filtration, secretion, and/or reabsorption profiles cannot be ruled out. Determination of renal clearance rates for all cannabinoid analytes and creatinine is required to further evaluate the impact of creatinine-normalization.

In occasional smokers creatinine-normalized and nonnormalized THCCOOH and THCCOOH-glucuronide concentrations increased after smoking when present. No substantial increase was noted in frequent smokers because most THCCOOH and THCCOOH-glucuronide originated from prior self-administered cannabis, masking increases from a single smoked dose. THCCOOH-glucuronide concentrations were much higher than THCCOOH concentrations in both groups (Table 1). Most immunoassays and screening tests target THCCOOH and have unknown glucuronide cross-reactivity; the only assay for which cross-reactivity was documented (Alere[TM]) had a reported cross-reactivity of 50%, possibly explaining the occurrence of some FN screening tests.

Nonnormalized, unconjugated THCCOOH concentrations in this study were much lower than previously reported, except for those reported by Kelly and Jones, who documented 4.3 and 1.0 [micro]g/L THCCOOH in frequent and infrequent smokers' mean 24-h pooled urine (13). Weinmann et al. documented THCCOOH from 43 to 455 [micro]g/L and THCCOOH-glucuronide from 300 to 1147 [micro]g/L. from THCCOOH concentrations before and after enzymatic hydrolysis (21). Felli et al. reported median (range) THCCOOH and THCCOOH-glucuronide concentrations of 17.2 (3.4-1426) [micro]g/L and 193 (26.0-7830) [micro]g/L, respectively, with direct LC-MS/MS analysis of workplace drug testing samples (IS). Skoppetal. (19) reported mean (SD) creatinine-normalized concentrations of THCCOOH and THCCOOH-glucuronide of 66 (72) and 1580 (1564) [micro]g/g, 9 (7) and 602 (545) [micro]g/g, and 3 (2) and 139 (92) [micro]g/g in frequent (several times/day), moderate (once/week to once/day), and occasional smokers (less than once/week), respectively, following direct analysis. Whereas Felli et al. (18) and Skopp et al. (19) stored samples at -20[degrees]C for unspecified time frames, Weinmann et al. did not report storage conditions. THCCOOH-glucuronide readily hydrolyzes to THCCOOH, producing up to 2- and 10-fold increases from baseline THCCOOH concentrations following 2-day storage at 4 [degrees]C and 20 [degrees]C, respectively; THC-COOH and THCCOOH-glucuronide were stable for at least 15 days at -20 [degrees]C (20). In our study, all samples were immediately refrigerated, frozen within 12 h, and analyzed on site generally within 24 h, minimizing THCCOOH formation during shipping or storage and possibly explaining our lower THCCOOH concentrations. Previous work documented acceptable stability of these cannabinoids following 3 freeze-thaw cycles (25). Total THCCOOH concentrations were consistent between our study and previously published studies.

[FIGURE 2 OMITTED]

It is unclear from these data how long THCCOOH can be detected in frequent smokers' urine because urine collection extended only 30 h postdose, when 62% of frequent smokers' nonnormalized THCCOOH was [greater than or equal to]1.2 [micro]g/L. Skopp et al. documented nonnormalized THCCOOH in frequent smokers (cannabis consumption several times/day) for at least 10 days (LOQ = 2 [micro]g/L) (19). However, initial THCCOOH concentrations were much higher in those participants compared to our study population. For occasional smokers, only 60% were ever THCCOOH positive, and all but 2 were negative in their last urine sample. One participant with a positive last sample had 5 THCCOOH-negative urine samples before the positive sample at 30 h. The presence of THCCOOH in 62% of frequent smokers for more than 30 h and its low prevalence in occasional smokers precludes THCCOOH's use as a marker of recent use in either group.

THC-GLUCURONIDE

Two reports documented THC-glucuronide analysis (16, 19). Whereas no nonnormalized THC-glucuronide was detected in occasional (less than once/month) smokers at a 2.3-[micro]g/L cutoff following paced smoking of a standardized 70-mg THC/cigarette, 30.4% of doping samples with THCCOOH >15 [micro]g/L were THC-glucuronide positive (2.3-29 [micro]g/L) (16). The concentrations reported in that work are similar to our THC-glucuronide concentrations (0-45.2 and 0-21.5 [micro]g/L in frequent and occasional smokers, respectively). However, our reported concentrations are higher than those reported by Skopp et al., who documented 1-6 [micro]g/L in frequent smokers' and no THC-glucuronide in occasional smokers' random urine samples (19). In our study, THC-glucuronide concentrations peaked immediately after smoking, returning to baseline concentrations within approximately 10 h (Fig. 1), explaining the lower detection rates and concentrations in random urine samples from Skopp et al. In creatinine-normalized samples, participant J exhibited an unusual increase in normalized THC-glucuronide concentrations before smoking that did not occur in his noncreatinine normalized samples; this increase was an artifact of a low urine creatinine concentration (11 mg/dL). Following its peak in urine, THC-glucuronide concentration paralleled its rapid decrease in plasma after smoking (32).

Other authors suggest that nonnormalized THC-glucuronide >2.3 [micro]g/L could differentiate incompetition from out-of-competition cannabis use (16). However, at our 2- and 5-[micro]g/L cutoffs, the time of last positive was >30 h in some frequent smokers, negating the utility of THC-glucuronide as a general marker of recent use. In frequent smokers, THC-glucuronide exceeded 0.5 [micro]g/L in all 14 smokers' last urine samples, precluding determination of time of last detection. We previously found extended unconjugated THC excretion ([greater than or equal to] 22.5 [micro]g/L, up to 24 days) in chronic daily smokers' urine samples following tandem enzymatic-alkaline hydrolysis (9). Because we found no unconjugated THC in urine in the present study, total THC detected in the previous study was most likely liberated from THC-glucuronide following hydrolysis. In occasional smokers, THC-glucuronide was detected for 1.3-23.2 h at the method's LOQ and for 1.3-7.1 h with a1l-[micro]g/L cutoff. Some occasional smokers were negative by 2 h and others had THC-glucuronide-negative urine samples interspersed between 2 positive samples within 20 h after smoking. Therefore, THC-glucuronide presence can be used as an inclusionary, but not exclusionary, marker of recent use, if there is clear evidence of occasional consumption.

MODEL OF RECENT USE

We describe here the utility of monitoring THC-glucuronide in consecutive urine samples to document cannabis smoking within 6 h (Table 4), a period of time closely mirroring the window of acute cannabis psychomotor impairment (33). Previous models used creatinine-normalized urine samples to evaluate if new cannabis smoking occurred between 2 samples bracketing potential cannabis use. To our knowledge, there are no methods of documenting recent use from samples collected shortly after smoking and without a prior baseline concentration, as would be the case when documenting potential impaired driving, new use in residential treatment facilities, accident investigations, and prohibited in-competition drug use in sports. When an individual is in custody or supervised for an extended period of time, the governing agency may be able to collect multiple urine samples. By collecting consecutive samples and setting new use criteria of absolute %differencc between the 2 consecutive samples of [greater than or equal to] 50% and a creatinine-normalized concentration of [greater than or equal to] 2 [micro]g/g in the first of the consecutive samples, we were able to identify recent cannabis smoking within 6 h of the first urine collection with high efficiency. This model had lower efficiency in occasional smokers because there were fewer consecutive positive THC-glucuronide samples. A criterion of [greater than or equal to] 2 [micro]g/g in the first of the consecutive samples was used to minimize FP that may occur given variability in urinary concentrations during extended excretion in frequent smokers. By using the absolute [greater than or equal to] 50% difference, the model allowed collection during the initial THC-glucuronide excretion phase, when THC-glucuronide may still be rising. There were 4.2% FP predictions in frequent smokers and 7.7% in occasional smokers. There were 1.0% FN predictions in frequent smokers and 15.4% in occasional smokers. FP and FN results were distributed evenly across individuals. All FN had absolute %differences of [greater than or equal to] 50%; however, lowering the criteria to a %difference of [greater than or equal to] 40% increased FP. In this proposed model, FP occurred when recent use (<6 h) was predicted but actual smoking occurred 6.4-11.5 h before the first of consecutive sample collections. Although considering only %difference has similar efficiency, the possibility of FP due to natural urinary concentration variability is higher. Consecutive urine samples were collected 0.3-8.3 h apart; the time between urine collections did not affect the model. Further model evaluation with a second set of data is needed.

We documented here simultaneous THCCOOH, THC-glucuronide, and THCCOOH-glucuronide analysis in frequent and occasional smokers following controlled smoked cannabis. THCCOOH, THC-glucuronide, and THCCOOH-glucuronide concentrations were significantly higher in frequent than occasional smokers. Furthermore, a creatinine-normalized THC-glucuronide absolute % difference >50% between 2 consecutive urine samples, with the first of the consecutive samples [greater than or equal to] 2 [micro]g/g, maybe used as a marker of recent smoking within 6 h of the first sample collection in frequent smokers. These data will improve urinary cannabinoid interpretation in clinical, drug treatment, law enforcement, sports doping, and workplace drug testing programs.

Acknowledgments: We acknowledge the contributions of the clinical staffs of the National Institute on Drug Abuse, Intramural Research Program, and Behavioral Pharmacology Research Unit and Clinical Research Unit, Johns Hopkins Bayview Medical Center, as well as Dr. David M. Schwope for protocol design assistance, Dan Nichols and the staff at the Forensic Toxicology Drug Testing Laboratory in Fort Meade who provided urine creatinine data, the Graduate Partnership Program, NIH, and the "Fondation Baxter et Alma Ricard." This research was funded by the Intramural Research Program, National Institute on Drug Abuse, NIH.

Author Contributions: All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 requirements: (a) significant contributions to the conception and design, acquisition of data, or analysis and interpretation of data; (b) drafting or revising the article for intellectual content, and (c) final approval of the published article.

Authors' Disclosures or Potential Conflicts of Interest: Upon manuscript submission, all authors completed the author disclosure form. Disclosures and/or potential conflicts of interest:

Employment or Leadership: None declared.

Consultant or Advisor)' Role: None declared.

Stock Ownership: None declared.

Honoraria: None declared.

Research Funding: Intramural Research Program of the National Institute on Drug Abuse, NIH.

Expert Testimony: None declared.

Patents: None declared.

Role of Sponsor: The funding organizations played no role in the design of study, choice of enrolled patients, review and interpretation of data, or preparation or approval of manuscript.

References

(1.) United Nations Office on Drugs and Crime (UNODC). World drug report 2013. http:// www.unodc.org/unodc/secured/wdr/wdr2013/ World_Drug_Report_2013.pdf (Accessed August 2013).

(2.) Hunt CA, Jones RT. Tolerance and disposition of tetrahydrocannabinol in man. J Pharmacol Exp Ther 1980;215:35-44.

(3.) Niedbala RS, Kardos KW, Fritch OF, Kardos S, Fries T, Waga J, et al. Detection of marijuana use by oral fluid and urine analysis following single-dose administration of smoked and oral marijuana. J Anal Toxicol 2001 ;25:289-303.

(4.) Manno JE, Manno BR, Kemp PM, Alford DD, Abukhalaf IK, McWilliams ME, et al. Temporal indication of marijuana use can be estimated from plasma and urine concentrations of delta9-tetrahydrocannabinol, 11-hydroxydelta9-tetrahydrocannabinol, and 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid. J Anal Toxicol 2001;25:538-49.

(5.) Gustafson RA, Levine B, Stout PR, Klette KL, George MP, Moolchan ET, Huestis MA. Urinary cannabinoid detection times following controlled oral administration of delta9-tetrahydrocannabinol to humans. Clin Chem 2003;49:1114-24.

(6.) Gustafson RA Kim I, Stout PR, Klette KL, George MP, Moolchan ET, et al. Urinary pharmacokinetics of 11 -nor-9-corboxy-delta9-tetrahydrocannabinol after controlled oral delta9-tetrahydrocannabinol administration. J Anal Toxicol 20[O.sub.4];28:160-7.

(7.) Glaz-Sandberg A, Dietz L, Nguyen H, Oberwittler H, Aderjan R, Mikus G. Pharmacokinetics of 11-nor-9-carboxy-delta(9)-tetrahydrocannabinol (CTHC) after intravenous administration of CTHC in healthy human subjects. Clin Pharmacol Ther 2007;82:63-9.

(8.) Goodwin RS, Darwin WD, Chiang CN, Shih M, Li S-H, Huestis MA. Urinary elimination of 11-nor-9-carboxy-delta9-tetrahydrocannabinol in cannabis users during continuously monitored abstinence. J Anal Toxicol 2008;32:562-6.

(9.) Lowe R, Abraham T, Darwin W, Herning R, Cadet J, Huestis M. Extended urinary Delta9-tetrahydrocannabinol excretion in chronic cannabis users precludes use as a biomarker of new drug exposure. Drug Alcohol Depend 2009; 105: 24-32.

(10.) Smith ML Barnes AJ, Huestis MA. Identifying new cannabis use with urine creatinine-normalized THCC00H concentrations and time intervals between specimen collections. J Anal Toxicol 2009;33:185-9.

(11.) Schwilke EW, Gullberg RG, Darwin WD, Chiang CN, Cadet JL, Gorelick DA, et al. Differentiating new cannabis use from residual urinary cannabinoid excretion in chronic, daily cannabis users. Addiction 2011;106:499-506.

(12.) Smith-Kielland A, Skuterud B, Morland J. Urinary excretion of 11-nor-9-carboxy-delta9-tetrahydrocannabinol and cannabinoids in frequent and infrequent drug users. J Anal Toxicol 1999;23:323-32.

(13.) Kelly P, Jones RT. Metabolism of tetrahydrocannabinol in frequent and infrequent marijuana users. J Anal Toxicol 1992;16:228-35.

(14.) Karschner E, Schwilke E, Lowe R, Darwin W, Pope H, Herning R, et al. Do Delta9-tetrahydrocannabinol concentrations indicate recent use in chronic cannabis users? Addiction 2009;1[O.sub.4]:2[O.sub.4]1-8.

(15.) Bergamaschi MM, Karschner EL Goodwin RS, Scheidweiler KB, Hirvonen J, Queiroz RH, Huestis MA. Impact of prolonged cannabinoid excretion in chronic daily cannabis smokers' blood on per se drugged driving laws. Clin Chem 2013;59: 519-26.

(16.) Mareck U, Haenelt N, Geyer H, Guddat S, Kamber M, Brenneisen R, et al. Temporal indication of cannabis use by means of THC glucuronide determination. Drug Test Anal 2009;1:505-10.

(17.) Mazur A, Lichti CF, Prather PL Zielinska AK, Bratton SM, Gallus-Zawada A, et al. Characterization of human hepatic and extrahepatic UDP-glucuronosyltransferase enzymes involved in the metabolism of classic cannabinoids. Drug Metab Dispos 2009;37:1496-5[O.sub.4].

(18.) Felli M, Martello S, Chiarotti M. LC-MS-MS method for simultaneous determination of THCCOOH and THCCOOH-glucuronide in urine: application to workplace confirmation tests. Forensic Sci Int 2011;2[O.sub.4]:67-73.

(19.) Skopp G, Potsch L, Gan/Jmann 8, Mauden M, Richter 8, Aderjan R, Mattem R. Freie und glucuronidierte Cannabinoide im Urin: Untersuchungen zur Einschatzung des Konsumverhaltens. Rechtsmedizin 1999;10:21-8.

(20.) Skopp G, Potsch L. An investigation of the stability of free and glucuronidated 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid in authentic urine samples. J Anal Toxicol 20[O.sub.4];28: 35-40.

(21.) Weinmann W, Vigt S, Goerke R, Muller C, Bromberger A. Simultaneous determination of THC-COOH and THC-COOH-glucuronide in urine samples by LC/MS/MS. Forensic Sci Int 2000.T13: 381-7.

(22.) Dietz L, Glaz-Sandberg A, Nguyen H, Skopp G, Mikus G, Aderjan R. The urinary disposition of intravenously administered 11-nor-9-carboxydelta-9-tetrahydrocannabinol in humans. Ther Drug Monit 2007;29:368-72.

(23.) Abraham TT, Lowe RH, Pirnay SO, Darwin WD, Huestis MA. Simultaneous GC-EI-MS determination of Delta9-tetrahydrocannabinol, 11-hydroxy-Delta9-tetrahydrocannabinol, and 11-nor-9carboxy-Delta9-tetrahydrocannabinol in human urine following tandem enzyme-alkaline hydrolysis. J Anal Toxicol 2007;31:477-85.

(24.) Kemp PM, Abukhalaf IK, Manno JE, Manno BR, Alford DD, McWilliams ME, et al. Cannabinoids in humans. II. The influence of three methods of hydrolysis on the concentration of THC and two metabolites in urine. J Anal Toxicol 1995; 19: 292-8.

(25.) Scheidweiler KB, Desrosiers NA, Huestis MA. Simultaneous quantification of free and glucuronidated cannabinoids in human urine by liquid chromatography tandem mass spectrometry. Clin Chim Acta 2012;413:1839-47.

(26.) Department of Health and Human Services (DHHS). Mandatory guidelines for federal workplace drug testing. Federal Register 2008;73:71858-907. http://www.gpo.gov/fdsys/pkg/FR-2008-11 -25/pdf/E8-26726.pdf (Accessed August 2013).

(27.) World Anti-Doping Agency (WADA). Decision limits for the confirmatory quantification of threshold substances. http://www.wada-ama.org/Documents/Worid_Anti-Doping_Program/WADP-IS-Laboratories/Technical_ Documents/WADA-TD2013DL-Decision-Limits-for-the-Confirmatory-Quantification-Threshold-Substances-2.0-EN.pdf (Accessed August 2013).

(28.) Bergamaschi MM, Barnes A, Queiroz RH, Hurd YL, Huestis MA. Impact of enzymatic and alkaline hydrolysis on CBD concentration in urine. Anal Bioanal Chem 2013;405:4679-89.

(29.) Watanabe K, Yamaori S, Funahashi T, Kimura T, Yamamoto I. Cytochrome P450 enzymes involved in the metabolism of tetrahydrocannabinol and cannabinol by human hepatic microsomes. Life Sci 2007;80:1415-9.

(30.) Garcia-Martin E, Martinez C, Ladero JM, Agundez JA. Interethnic and intraethnic variability of CYP2C8 and CYP2C9 polymorphisms in healthy individuals. Mol Diagn Ther 2006;10:29-40.

(31.) Wall ME, Sadler 8M, Brine D, Taylor H, Perez-Reyes M. Metabolism, disposition, and kinetics of delta-9-tetrahydrocannabinol in men and women. Clin Pharmacol Ther 1983;34:352-63.

(32.) Schwope DM, Karschner EL, Gorelick DA, Huestis MA. Identification of recent cannabis use: whole-blood and plasma free and glucuronidated cannabinoid pharmacokinetics following controlled smoked cannabis administration. Clin Chem 2011;57:1406-14.

(33.) Ramaekers JG, Moeller MR, van Ruitenbeek P, Theunissen EL, Schneider E, Kauert G. Cognition and motor control as a function of Delta9-THC concentration in serum and oral fluid: limits of impairment. Drug Alcohol Depend 2006;85: 114-22.

Nathalie A. Desrosiers, [1,2] Dayong Lee, [1,2] Marta Concheiro-Guisan, [1] Karl B. Scheidweiler, [1] David A. Gorelick, [1] and Marilyn A. Huestis [1] *

[1] Chemistry and Drug Metabolism Section, NIDA IRP, Baltimore, MD; [2] Program in Toxicology, University of Maryland Baltimore, Baltimore, MD.

* Address correspondence to this author at: Chemistry and Drug Metabolism, Intramural Research Program. National Institute on Drug Abuse, National Institutes of Health, 251 Bayview Blvd., Suite 200 Rm. 05A-721, Baltimore, MD 21224. Fax 443-740-2823; e-mail mhuestis@intra.nida.nih.gov.

Previous presentation of the manuscript: 65th Annual Conference of the American Academy of Forensic Sciences, Washington, D.C., February 2013.

Received August 2, 2013; accepted October 3, 2013.

Previously published online at DOI: 10.1373/clinchem.2013.214106

[3] Nonstandard abbreviations: THC, A9-tetrahydrocannabinol; THCCOOH, 11-nor9-carboxy-THC; 11-OH-THC, 11-hydroxy-THC; CBD, cannabidiol; CBN, cannabinol; LC-MS/MS, liquid chromatography-tandem mass spectrometry; LOQ, Limit of quantification; TP, true positive; TN. true negative; FP, false positive; FN, false negative.
Table 1. Median (range) concentrations in 6-h time windows in 14
frequent and 10 occasional smokers following a single smoked 6.8%
THC cigarette.

Analyte                   Time        Frequent          Frequent
                        window, h   smokers, no.        smokers,
                                     of samples      concentrations

THCCOOH,                -19 to 0         70          3.6 (0 to 47.6)
[micro]g/L               0 to 6          26          2.6 (0 to 15.4)
                         6 to 12         37          2.1 (0 to 36.6)
                        12 to 18         26          1.6 (0 to 16.2)
                        18 to 24         27          5.0 (0 to 24.0)
                        24 to 30         51           0 (0 to 6.3)

THC-glucuronide,        -19 to 0         70          2.9 (0 to 47.5)
[micro]g/L               0 to 6          26         9.4 (2.9 to 45.2)
                         6 to 12         37          2.2 (0 to 12.8)
                        12 to 18         26          2.5 (0 to 7.7)
                        18 to 24         27         3.2 (1.2 to 20.4)
                        24 to 30         51          1.1 (0 to 7.5)
THCCOOH-glucuronide,    -19 to 0         70        252 (10.5 to 1660)
[micro]g/L               0 to 6          26        238 (10.4 to 1095)
                         6 to 12         37         289 (40 to 2080)
                        12 to 18         26         138 (16.7 to 735)
                        18 to 24         27         204(39.1 to 915)
                        24 to 30         51         101 (17.1 to 333)
Total THCCOOH,          -19 to 0         70         170 (6.9 to 1112)
[micro]g/l               0 to 6          26         166 (6.9 to 734)
                         6 to 12         37        127 (26.5 to 1413)
                        12 to 18         26        92.7 (11.0 to 496)
                        18 to 24         27        139 (27.0 to 626.6)
                        24 to 30         51        68.1 (11.3 to 225)
Creatinine-normalized   -19 to 0         70          3.3 (0 to 30.8)
THCCOOH, [micro]g/g      0 to 6          26          2.8 (0 to 13.4)
                         6 to 12         37          2.0 (0 to 20.7)
                        12 to 18         26          1.4 (0 to 17.2)
                        18 to 24         27          4.6 (0 to 22.1)
                        24 to 30         51            0(0 to 6.8)
Creatinine-normalized   -19 to 0         70          2.5 (0 to 29.7)
THC-glucuronide,         0 to 6          26         12.3 (2.2 to 121)
[micro]gig               6 to 12         37          3.0 (0 to 7.6)
                        12 to 18         26          2.6 (0 to 6.4)
                        18 to 24         27         2.7 (1.3 to 7.4)
                        24 to 30         51          2.2 (0 to 6.9)
Creatinine-normalized   -19 to 0         70         203 (64.6 to 949)
THCCOOH-glucuronide,     0 to 6          26         212(93.1 to 1166)
[micro]g/g               6 to 12         37        238 (67.8 to 1174)
                        12 to 18         26         160 (69.2 to 458)
                        18 to 24         27         140 (77.6 to 418)
                        24 to 30         51         147 (55.2 to 501)
Creatinine-normalized   -19 to 0         70         137 (42.7 to 640)
total THCCOOH,           0 to 6          26         143 (63.9 to 782)
[micro]g/g               6 to 12         37         161 (44.9 to 798)
                        12 to 18         26         108 (45.8 to 311)
                        18 to 24         27         102 (55.9 to 292)
                        24 to 30         51        99.6 (36.5 to 338)

Analyte                   Time       Occasional        Occasional
                        window, h   smokers, no.        smokers,
                                     of samples      concentrations

THCCOOH,                -19 to 0         56                 0
[micro]g/L               0 to 6          25           0 (0 to 4.8)
                         6 to 12         20           0 (0 to 4.4)
                        12 to 18         18           0 (0 to 1.4)
                        18 to 24         18           0 (0 to 4.8)
                        24 to 30         38           0 (0 to 1.4)

THC-glucuronide,        -19 to 0         56           0 (0 to 8.2)
[micro]g/L               0 to 6          25          1.3 (0 to 21.5)
                         6 to 12         20           0 (0 to 2.0)
                        12 to 18         18                 0
                        18 to 24         18           0 (0 to 0.9)
                        24 to 30         38                 0
THCCOOH-glucuronide,    -19 to 0         56           0 (0 to 34.8)
[micro]g/L               0 to 6          25          16.0 (0 to 119)
                         6 to 12         20          40.6 (0 to 195)
                        12 to 18         18         25.4 (0 to 60.7)
                        18 to 24         18         15.8 (6.6 to 214)
                        24 to 30         38          11.3 (0 to 100)
Total THCCOOH,          -19 to 0         56            0 (0 to 23)
[micro]g/l               0 to 6          25         10.6 (0 to 81.6)
                         6 to 12         20          27.5 (0 to 134)
                        12 to 18         18        16.8 (4.4 to 146.4)
                        18 to 24         18         12.8 (4.4 to 146)
                        24 to 30         38          7.4 (0 to 66.2)
Creatinine-normalized   -19 to 0         56                 0
THCCOOH, [micro]g/g      0 to 6          25           0 (0 to 5.9)
                         6 to 12         20           0 (0 to 5.5)
                        12 to 18         18           0 (0 to 1.4)
                        18 to 24         18           0 (0 to 3.2)
                        24 to 30         38           0 (0 to 1.3)
Creatinine-normalized   -19 to 0         56           0 (0 to 6.5)
THC-glucuronide,         0 to 6          25          4.1 (0 to 35.1)
[micro]gig               6 to 12         20           0 (0 to 4.0)
                        12 to 18         18                 0
                        18 to 24         18           0 (0 to 0.8)
                        24 to 30         38                 0
Creatinine-normalized   -19 to 0         56           0 (0 to 33.7)
THCCOOH-glucuronide,     0 to 6          25          32.3 (0 to 258)
[micro]g/g               6 to 12         20          65.8 (0 to 305)
                        12 to 18         18          72.3 (0 to 147)
                        18 to 24         18         20.5 (8.9 to 146)
                        24 to 30         38          32.2 (0 to 128)
Creatinine-normalized   -19 to 0         56           0 (0 to 22.3)
total THCCOOH,           0 to 6          25          21.4 (0 to 175)
[micro]g/g               6 to 12         20          44.4 (0 to 202)
                        12 to 18         18         47.9 (0 to 97.0)
                        18 to 24         18        13.6 (5.9 to 99.3)
                        24 to 30         38         23.5 (0 to 85.0)

Table 2. Median (range) maximal concentrations in 14 frequent and
10 occasional cannabis smokers following a single smoked 6.8% THC
cigarette.

Parameter        Analyte                       Frequent
                                                smokers

Predose          THCCOOH (a)                14.2 (3.0-47.6)
maximal          THC-glucuronide (a,b)      10.0 (2.4-47.5)
concentration,   THCCOOH-glucuronide (a)     496 (272-1660)
[micro]g/L       Total THCCOOH (a,c)         343 (189-1112)

Predose          THCCOOH (a)                 7.6 (1.6-30.8)
maximal          THC-glucuronide (a,b)       8.1 (1.4-29.7)
concentration    THCCOOH-glucuronide (a)     296 (119-949)
(creatinine      Total THCC00H (a)           206 (80.1-640)
normalized),
[micro]g/g

Postdose         THCCOOH (a)                 9.2 (3.5-36.6)
maximal          THC-glucuronide (a,b)      15.0 (6.3-45.2)
concentration,   THCCOOH-glucuronide (a)     338 (147-2080)
[micro]g/L       Total THCCOOH (a)           233 (100-1413)

Postdose         THCCOOH (a)                 5.4 (2.7-22.1)
maximal          THC-glucuronide (a,b)      17.3 (7.2-121)
concentration    THCCOOH-glucuronide (a)     254 (145-1174)
(creatinine      Total THCCOOH (a)           183 (98.5-798)
normalized),
[micro]g/g

                                                               Test
                                                              statis-
Parameter        Analyte                      Occasional      tic, U
                                                smokers

Predose          THCCOOH (a)                       0             0
maximal          THC-glucuronide (a,b)         0 (0-8.2)        6.0
concentration,   THCCOOH- glucuronide (a)     0 (0-34.8)         0
[micro]g/L       Total THCCOOH (a,c)          0 (0-23.0)         0

Predose          THCCOOH (a)                       0             0
maximal          THC-glucuronide (a,b)         0 (0-6.5)        6.0
concentration    THCCOOH-glucuronide (a)       0 (0-34)          0
(creatinine      Total THCC00H (a)            0 (0-22.3)         0
normalized),
[micro]g/g

Postdose         THCCOOH (a)                  1.5 (0-4.8)        6
maximal          THC-glucuronide (a,b)      8.9 (1.3-21.5)     30.5
concentration,   THCCOOH-glucuronide (a)    74.2 (8.7-214)       4
[micro]g/L       Total THCCOOH (a)          50.1 (5.8-146)       4

Postdose         THCCOOH (a)                  1.7 (0-5.9)        9
maximal          THC-glucuronide (a,b)      15.2 (3.0-35.1)     32
concentration    THCCOOH-glucuronide (a)    67.3 (20.8-305)     15
(creatinine      Total THCCOOH (a)          45.3(13.8-202)      23
normalized),
[micro]g/g

                                                          Exact
Parameter        Analyte                    Effect    significance,
                                            size, r   2-tailed (p)

Predose          THCCOOH (a)                -0.868       <0.001
maximal          THC-glucuronide (a,b)      -0.779       <0.001
concentration,   THCCOOH- glucuronide (a)   -0.843       <0.001
[micro]g/L       Total THCCOOH (a,c)        -0.843       <0.001

Predose          THCCOOH (a)                -0.869       <0.001
maximal          THC-glucuronide (a,b)      -0.779       <0.001
concentration    THCCOOH-glucuronide (a)    -0.843       <0.001
(creatinine      Total THCC00H (a)          -0.843       <0.001
normalized),
[micro]g/g

Postdose         THCCOOH (a)                -0.766       <0.001
maximal          THC-glucuronide (a,b)      -0.437        <0.05
concentration,   THCCOOH-glucuronide (a)    -0.789       <0.001
[micro]g/L       Total THCCOOH (a)          -0.789       <0.001

Postdose         THCCOOH (a)                -0.731       <0.001
maximal          THC-glucuronide (a,b)      -0.418        <0.05
concentration    THCCOOH-glucuronide (a)    -0.657        <0.01
(creatinine      Total THCCOOH (a)          -0.562        <0.01
normalized),
[micro]g/g

(a) Significant differences between occasional and frequent
smokers.

(b) Participant H excluded from calculation because urine first
void after smoking was not collected.

(c) Total THCCOOH (molar sum of THCCOOH and THCCOOH-glucuronide,
equivalent to total THCCOOH following hydrolysis).

Table 3. Median (range) detection rates and time of last positive
at various cutoffs in 13 frequent and 10 occasional cannabis
smokers following controlled smoked 6.8% THC cigarette.

                                     Frequent smokers

                                    %              Time of
                               Participant      last positive
                                   ever        (among positive
                                positive        participants),
Analyte       Cutoff           (n = 13) (a)         h (b)

THCCOOH       1 [micro]g/L         100        >30 (23.5 to >30)
              2 [micro]g/L         100        27.5 (20.2 to >30)
              5 [micro]g/L          76.9      23.0 (6.8 to >30)
              2 [micro]g/g         100        27.5 (20.2 to >30)
              5 [micro]g/g          61.5      25.7 (20.2 to >30)

THC-          0.5 [micro]g/L       100               >30
glucuronide   1 [micro]g/L         100        >30 (27.5 to >30)
              2 [micro]g/L         100        24.5 (20.2 to >30)
              5 [micro]g/L         100         6.6 (1.4 to >30)
              2 [micro]g/g         100         >30 (1.6 to >30)
              5 [micro]g/g          92.3       4.9 (1.4 to >30)

THCCOOH-      5 [micro]g/L         100               >30
glucuronide

Total         15 [micro]g/L        100               >30
THCCOOH (c)   175 [micro]g/L        84.6      20.2 (4.8 to >30)

                                 Frequent      Occasional
                                 smokers        smokers

                                    %              %
                               Participants   Participants
                                   with           ever
                                 positive       positive
Analyte       Cutoff            last urine      (n = 10)

THCCOOH       1 [micro]g/L         61.5            60
              2 [micro]g/L         46.2            30
              5 [micro]g/L          7.7             0
              2 [micro]g/g         38.5            40
              5 [micro]g/g          7.7            10

THC-          0.5 [micro]g/L       100            100
glucuronide   1 [micro]g/L         92.3           100
              2 [micro]g/L         46.2            90
              5 [micro]g/L         23.1            60
              2 [micro]g/g         76.1           100
              5 [micro]g/g          7.7            80

THCCOOH-      5 [micro]g/L         100            100
glucuronide

Total         15 [micro]g/L        100             80
THCCOOH (c)   175 [micro]g/L       15.4             0

                                      Occasional smokers

                                                        %
                                   Time of         Participants
                                last positive          with
                               (among positive       positive
Analyte       Cutoff           participants) (h)    last urine

THCCOOH       1 [micro]g/L     22.7 (6.8 to >30)        20
              2 [micro]g/L     7.1 (6.8 to 22.1)        0
              5 [micro]g/L                              0
              2 [micro]g/g     14.6 (6.5 to >30)        10
              5 [micro]g/g            7.1               0

THC-          0.5 [micro]g/L   6.4 (1.3 to 23.2)        0
glucuronide   1 [micro]g/L     3.6 (1.3 to 7.1)         0
              2 [micro]g/L     2.6 (1.0 to 3.4)         0
              5 [micro]g/L     2.8 (1.5 to 3.4)         0
              2 [micro]g/g     3.0 (1.3 to 6.5)         0
              5 [micro]g/g     2.5 (1.5 to 3.4)         0

THCCOOH-      5 [micro]g/L     >30 (23.5 to >30)        80
glucuronide

Total         15 [micro]g/L    24.9 (6.4 to >30)        30
THCCOOH (c)   175 [micro]g/L                            0

(a) Participant B excluded from calculation because he left 26 h
after smoking.

(b) Last sample still positive indicated by >30 h.

(c) Total THCCOOH (molar sum of THCCOOH and THCCOOH-glucuronide,
equivalent to total THCCOOH following hydrolysis).

Table 4. Evaluation of multiple criteria to identify recent
cannabis smoking (within 6 h of first sample collection) in
sequential THC-glucuronide positive samples.

                             % Difference       % Difference
                           [greater than or   [greater than or
                            equal to] 40%      equal to] 50%
              Parameter    absolute change    absolute change

Overall      TP                   29                 29
             TN                  109                114
             FP                   14                  8
             FN                    7                  6
             Total               159                157
             Sensitivity          80.6               82.9
             Specificity          88.6               93.4
             Efficiency           86.8               91.1
Frequent     TP                   22                 22
             TN                  107                112
             FP                   12                  6
             FN                    5                  4
             Total               146                144
             Sensitivity          81.5               84.6
             Specificity          89.9               94.9
             Efficiency           88.4               93.1
Occasional   TP                    7                  7
             TN                    2                  2
             FP                    2                  2
             FN                    2                  2
             Total                13                 13
             Sensitivity          77.8               77.8
             Specificity          50.0               50.0
             Efficiency           69.2               69.2

                                                % Difference
                                              [greater than or
                                               equal to] 50%
                                              absolute change
                             % Difference      and 1st sample
                           [greater than or   [greater than or
                            equal to] 60%       equal to] 1
              Parameter    absolute change      [micro]g/mg

Overall      TP                   28                 29
             TN                  117                114
             FP                    5                  8
             FN                    7                  7
             Total               157                158
             Sensitivity          80.0               80.6
             Specificity          95.9               93.4
             Efficiency           92.4               90.5
Frequent     TP                   21                 22
             TN                  114                112
             FP                    4                  6
             FN                    5                  5
             Total               144                145
             Sensitivity          80.8               81.5
             Specificity          96.6               94.9
             Efficiency           93.8               92.4
Occasional   TP                    7                  7
             TN                    3                  2
             FP                    1                  2
             FN                    2                  2
             Total                13                 13
             Sensitivity          77.8               77.8
             Specificity          75.0               50.0
             Efficiency           76.9               69.2

                             % Difference       % Difference
                           [greater than or   [greater than or
                            equal to] 50%      equal to] 50%
                           absolute change    absolute change
                            and 1st sample     and 1st sample
                           [greater than or   [greater than or
                             equal to] 2        equal to] 3
              Parameter      [micro]g/mg        [micro]g/mg

Overall      TP                   29                 27
             TN                  115                116
             FP                    7                  6
             FN                    6                  8
             Total               157                157
             Sensitivity          82.9               77.1
             Specificity          94.3               95.1
             Efficiency           91.7               91.1
Frequent     TP                   22                 20
             TN                  112                113
             FP                    6                  5
             FN                    4                  6
             Total               144                144
             Sensitivity          84.6               76.9
             Specificity          94.9               95.8
             Efficiency           93.1               92.4
Occasional   TP                    7                  7
             TN                    3                  3
             FP                    1                  1
             FN                    2                  2
             Total                13                 13
             Sensitivity          77.8               77.8
             Specificity          75.0               75.0
             Efficiency           76.9               76.9

                             % Difference
                           [greater than or
                            equal to] 40%
                           absolute change
                            and 1st sample
                           [greater than or
                             equal to] 2
              Parameter      [micro]g/mg

Overall      TP                   29
             TN                  110
             FP                   12
             FN                    7
             Total               158
             Sensitivity          80.6
             Specificity          90.2
             Efficiency           88.0
Frequent     TP                   22
             TN                  107
             FP                   11
             FN                    5
             Total               145
             Sensitivity          81.5
             Specificity          90.7
             Efficiency           89.0
Occasional   TP                    7
             TN                    3
             FP                    1
             FN                    2
             Total                13
             Sensitivity          77.8
             Specificity          75.0
             Efficiency           76.9
COPYRIGHT 2014 American Association for Clinical Chemistry, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2014 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:Drug Monitoring and Toxicology
Author:Desrosiers, Nathalie A.; Lee, Dayong; Concheiro-Guisan, Marta; Scheidweiler, Karl B.; Gorelick, Davi
Publication:Clinical Chemistry
Article Type:Report
Date:Feb 1, 2014
Words:7858
Previous Article:Calcineurin activity assay measurement by liquid chromatography-tandem mass spectrometry in the multiple reaction monitoring mode.
Next Article:Newborn blood spot screening for sickle cell disease by using tandem mass spectrometry: implementation of a protocol to identify only the disease...
Topics:

Terms of use | Copyright © 2018 Farlex, Inc. | Feedback | For webmasters