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Työ- ja opiskelupaikkojen huumetestaus paranee - Kannabiksen testauksessa nyt voi erottaa uuden käytön "vanhasta" jäännekäytöstä

Kannabiksen käyttöä seurataan huumeseuloilla, joissa kannabiksen pitkästä metabolia-ajasta ( jopa 6 vkoa) johtuen, käyttäjät ovat voineet vedota siihen, että huumetestauksen kannabiksen positiivinen tulos on vanhan käytön seurausta, eikä enää ole ketomansa mukaan käyttäjä käyttänyt kannabista.

Nyt uusi analyysimenetelmä erottelee sen, onko kannabiksen käyttö uutta vai "vanhaa" käyttöä, eikä mitään entisiä käyttöresiduaaleja. Uusi menetelmä tarjoaa aivan uudenlaisia mahdollisuuksia myös työ- ja opiskelupaikkojen huumetestaukseen sekä opiaattikorvaushoitojen oheiskäytön seurantaan.

Eugene W. Schwilke,et al, Differentiating new cannabis use from residual urinary
cannabinoid excretion in chronic, daily cannabis users,
Addiction, Vol 106, Issue 3, pages 499–506, March 2011.


ABSTRACT
Aims To develop and validate empirically a mathematical model for identifying new cannabis use in chronic, daily cannabis smokers.

Design Models were based on urinary creatinine-normalized (CN) cannabinoid excretion in chronic cannabis smokers.

Setting Formodel development, participants resided on a secure research unit for 30 days.
For model validation, participants were abstinent with daily observed urine specimens for 28 days.

Participants A total of 48 (model development) and 67 (model validation) daily cannabis smokerswere recruited.

Measurements All voided urine was collected and analyzed for 11-nor-9-carboxy-D9-tetrahydrocannabinol (THCCOOH) by gas chromatography-mass spectrometry (GCMS; limit of quantification 2.5 ng/ml) and creatinine (mg/ml). Urine THCCOOH was normalized to creatinine, yielding ng/mg CN-THCCOOH concentrations. Urine concentration ratios were determined from 123 513 specimen pairs collected 2–30 days apart.

Findings Amono-exponential model (with two parameters, initial urine specimen CN-THCCOOH concentration and time between specimens), based on the Marquardt–Levenberg algorithm, provided a reasonable data fit. Prediction intervals with varying probability levels(80, 90, 95, 99%) provide upper ratio limits for each urine specimen pair. Ratios above these limits suggest cannabis re-use. Disproportionate numbers of ratios were higher than expected for some participants, prompting development of two additional rules that avoid misidentification of re-use in participants with unusual CN-THCCOOH excretion patterns.

Conclusions For the first time, a validated model is available to aid in the differentiation of new cannabis use
from residual creatinine-normalized 11-nor-9-carboxy-D9-tetrahydrocannabinol (CN-THCCOOH) excretion in
chronic, daily cannabis users. These models are valuable for clinicians, toxicologists and drug treatment staff and work-place, military and criminal justice drug-testing programs.