"Intra- and Intersubject Whole Blood/Plasma Cannabinoid Ratios Determined by 2-Dimensional, Electron Impact GC-MS with Cryofocusing" https://pmc.ncbi.nlm.nih.gov/articles/PMC3197018/
If the results of this study are accurate, it might have implications for the whole chain of events. When blood samples fortified with cannabinoids are stored at - 20°C, THC will deteriorate in storage and the analysis will detect a significantly lower amount of THC.
If the studies selected for determining the impairment limits have stored the blood samples at - 20°C, the impairment limits are likely pegged to a lower THC-level than what was factual at the time of collecting the blood samples. The courts will punish by an artificially low standard.
At the bottom of this page there is a list of studies involved. From the studies I have access to, blood samples have been stored at - 20°C. I have yet to find a study that is done 100 % correct. One study does both 4°C and - 20°C.
It would be an aggravating circumstance if blood samples from suspects tried in courts are stored at correct temperatures. The suspects will be tried in court with reliable blood levels which will be measured up to an artificially low legal standard.
There is mention of police and lab routines in relation to blood samples taken from suspects apprehended by the Norwegian police in a recent article. (1) Relevant quote: "The blood samples were sent to our laboratory by mail or by road transportation services and stored at 2–8 °C until analyzed."
A special thanks to defence attourney Torkjell Øvrebø, who helped me free of charge with legal material to understand the situation at hand. I recommend his article:
Sources
(1) https://www.sciencedirect.com/science/article/abs/pii/S0379073817301433?via%3Dihub
"THC and CBD in blood samples and seizures in Norway: Does CBD affect THC-induced impairment in apprehended subjects?"
When subjects are apprehended by the police in Norway on suspicion of drug use in connection to a crime, they are usually subjected to a blood test. The blood samples included in this study were whole blood drained into 5 mL BD Vacutainer® evacuated blood collection tubes, containing 20 mg of sodium fluoride and 143 IU of heparin (BD Diagnostics, Plymouth, UK). The blood samples were sent to our laboratory by mail or by road transportation services and stored at 2–8 °C until analyzed."
The expert commission and their sources
Avaliable for download is the report from the expert commission. The sources for Cannabis/THC will be lined up below. The numbers set up as [13] is the numbers used in the report to denote sources. I will mark in bold quotes from sources where the blood samples are stored at wrong or correct temperatures.
[13] http://www.grotenhermen.com/driving/mura.pdf
Comparison of the prevalence of alcohol, cannabis and other drugs between 900 injured drivers and 900 control subjects: results of a French collaborative study. "Blood samples were collected in 10 ml glass tubes with lithium heparinate and kept at 4°C for analysis within 48 h or otherwise frozen at -20°C. "
[14] https://www.sciencedirect.com/science/article/abs/pii/S0001457502001537?via%3Dihub
The involvement of drugs in drivers of motor vehicles killed in Australian road traffic crashes. Have not found access, but believe correct method has been used. (Update: storage temperature not disclosed. Detective work is possible))
[17] https://www.bmj.com/content/331/7529/1371
Cannabis intoxication and fatal road crashes in France: population based case-control study
Does not disclose storage temperature of blood samples. Detective work is possible.
[18] https://www.csus.edu/faculty/m/fred.molitor/docs/marijuana%20and%20car%20crash%20injury.pdf
Marijuana use and car crash injury
"Self reported marijuana use in the 3 hours prior to the crash/ survey and habitual marijuana use over the previous 12 months were recorded, along with a range of other variables potentially related to crash risk. The main outcome measure was hospitalization or death of a vehicle occupant due to car crash injury."
[29] https://pubmed.ncbi.nlm.nih.gov/17916224/
Developing limits for driving under cannabis
"An international working group of experts on issues related to drug use and traffic safety evaluated evidence from experimental and epidemiological research and discussed potential approaches to developing per se limits for cannabis." Meta study.
Method control for reference list:
1 Heishman S. J., Singleton E. G., Crouch D. J. Laboratory validation study of drug evaluation and classification program: ethanol, cocaine, and marijuana. J Anal Toxicol 1996; 20: 468–83. "Blood samples were collected on ice ... storage at - 20 C"
2 Heishman S. J., Singleton E. G., Crouch D. J. Laboratory validation study of drug evaluation and classification program: alprazolam, d-amphetamine, codeine, and marijuana. J Anal Toxicol 1998; 22: 503–14. "Blood samples were collected on ice ... Samples were stored at - 20 C and shipped frozen on dry ice.."
5 Mason A. P., Perez-Reyes M., McBay A. J., Foltz R. L. Cannabinoid concentrations in plasma after passive inhalation of marijuana smoke. J Anal Toxicol 1983; 7: 172–4. "The plasma specimens obtained were kept frozen at -20 C until analyzed.
7 Grotenhermen F. Pharmacokinetics and pharmacodynamics of cannabinoids. Clin Pharmacokin 2003; 42: 327–60. Meta study
8 Bates M. N., Blakely T. A. Role of cannabis in motor vehicle crashes. Epidemiol Rev 1999; 21: 222–32. Meta study, with or without alcohol.
[69] https://www.ukcia.org/research/DoseRelatedRiskOfCrashes.pdf
Dose related risk of motor vehicle crashes after cannabis use
Meta study.
[108] https://pubmed.ncbi.nlm.nih.gov/12404625/
Marijuana, alcohol and actual driving performance
"On separate evenings they were given weight calibrated Delta(9)-tetrahydrocannabinol (THC) doses of 0, 100 and 200 &mgr;g/kg with and without an alcohol dose sufficient for achieving blood alcohol concentrations (BAC) of 0.04 g/dl while performing a Road Tracking and Car Following Test in normal traffic."
[109] https://pubmed.ncbi.nlm.nih.gov/20380913/
The effects of cannabis and alcohol on simulated arterial driving: Influences of driving experience and task demand
"Cannabis was administered by inhalation of smoke from pre-rolled cannabis cigarettes (supplied by the National Institute of Drug Abuse, USA). Active cigarettes contained 19 mg delta-9-THC. Using a counterbalanced design, the simulated driving performance of 25 experienced and 22 inexperienced drivers was tested..."
[110] https://pubmed.ncbi.nlm.nih.gov/18460360/
Effects of THC on driving performance, physiological state and subjective feelings relative to alcohol
"We tested the subjective feelings and driving abilities after placebo, smoking two dosages of THC (13 mg and 17 mg), drinking (0.05% BAC) and 24 h after smoking the high dose THC cigarette, while monitoring physiological activity of the drugs by heart rate. Fourteen healthy students, all recreational marijuana users, participated in the study."
[111] https://trid.trb.org/view/470117
MARIJUANA'S EFFECTS ON ACTUAL DRIVING PERFORMANCE
"Subjects were treated on separate occasions with THC 100, 200 and 300 microgram per kilogram, and placebo. They performed a 22-km road tracking test beginning 30 and 90 minutes after smoking."
"We selected nine studies in the review and meta-analysis."
[112] https://www.erowid.org/plants/cannabis/cannabis_driving5.shtml#document_header
Marijuana, Alcohol and Actual Driving Performance
"On separate evenings they were given weight.calibrated doses of THC and alcohol, or placebos for one or both substances as follows: alcohol placebo + THC placebo; alcohol placebo + THC 100 ~g/kg; alcohol placebo + THC 200 1lg/kg; alcohol + THC placebo; alcohol +THC 100 ~g/kg; and, alcohol +THC 200 1lg/kg. The initial alcohol dose was sufficient for achieving a peak blood alcohol concentration (BAC) of about 0.07 g/dl. Booster doses were later given to sustain BAC around 0.04 g/dl during testing. THC was administered by smoking marijuana cigarettes (2.2 and 3.95% THC from the US National Institute on Drug Abuse, NIDA) which had been weight.calibrated by cutting. Initial drinking preceded smoking by 60 min."
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From initial article:
"It is unclear whether poor stability of cannabinoids during storage results from chemical degradation or whether compounds become irreversibly bound to container surfaces or whole-blood precipitate."
"To our knowledge, this is the first published report of this finding and the first to describe whole-blood stability in polypropylene containers. Instability during frozen storage possibly could result from cannabinoid binding to denatured proteins and/or adsorption to container surfaces. At room temperature, analytes also may degrade, bind to denatured proteins, or adsorb to container surfaces. Comparative stability at 4°C possibly may result because whole-blood proteins remain intact, analyte degradation is less likely, and plasma protein binding may prevent adsorption to polypropylene."
BONUS INFORMATION:
Some studies choose to determine THC in plasma while legal standards in most countries use THC in whole blood.
"Comparison of whole-blood/plasma cannabinoid ratios has rarely been determined from simultaneously collected specimens. THC whole-blood-to-plasma ratio was 0.46 in simultaneously collected fresh plasma specimens analyzed shortly after collection and whole-blood specimens analyzed after storage for 8 months (10). Whole-blood-to-plasma ratios in 8 subjects after controlled cannabis smoking were 0.66 (0.06), 0.76 (0.14), and 0.61 (0.08) for THC, 11-OH-THC, and THCCOOH, respectively, whereas in postmortem whole-blood and serum specimens collected at autopsy, cannabinoid ratios were <0.52 for all analytes (11)."