Abstract
Cannabis is the most widely used illicit drug in New Zealand. About 4 years ago schools in New Zealand began introducing drug programmes in order ascertain a pupil's likely cannabinoid use. Our toxicology laboratory screened such specimens for the presence of cannabinoids, using CEDIA ® immunoassay, at a cut-off of 50 ng/mL as directed by the AS/NZS 4308:2001 standard. However, the consequent result that we reported, as not detected (<50 ng/mL), in many cases did not parallel the pupil's confessed cannabis use. Our laboratory has therefore used a lower cut-off of 25 ng/mL, by this immunoassay. We use this cut-off only for non-evidential analyses. Stored specimens were analysed over two time periods. Initially 2359 urine samples were screened for cannabinoids. 130 of these specimens had a value between 25 and 49 ng/mL and 60 of this group were randomly selected for confirmation by GC–MS. In all the 60 specimens, the presence of THCCOOH was confirmed. A further 760 specimens were collected over a later time period. Of these, 48 specimens had an immunoassay value of 25–49 ng/mL and all 48 specimens were confirmed positive for THCCOOH by GC–MS. This study indicates that the CEDIA ® THCPLUS immunoassay can be used to screen for the presence of urinary cannabinoids using a 25 ng/mL cut-off. Use of such a cut-off will limit the occurrence of false negative cannabinoid screening results. For school children a lower cut-off may be important, as consequent remedial action, following a positive immunoassay result, may limit the adverse outcomes such as dependence and impairment of achievements as suggested in a New Zealand study by Fergusson and Joseph.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call