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Discrepancies in Washington Cannabis Lab Test Results Reveal Systemic Failings

By Leo Bear-McGuiness
Published: Jul 19, 2018   
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There are clear, systematic differences within the results provided by cannabis testing laboratories in the Washington state area, according to recent research published in Nature Scientific Reports. Given the variety of pharmacologically active compounds in cannabis products, it is vital that users are accurately informed on the biochemical profile of the cannabis they are consuming. Such accuracy and reliability necessitate more stringent and standardized laboratory testing across the USA, which the researchers behind the paper highly recommend.

Through their efforts, the researchers also found evidence that commercial cannabis variants found in Washington fall into three principal chemotypes defined by their THC: CBD ratio, as many have presumed. However, when it came to analyzing the most popularized “strains”, which include both indica and sativa, the researchers found no substantial differences in the THC or CBD content between flower samples. Indicating that these labels may have less meaning than widely thought, at least as far as THC and CBD contents are concerned.

The researchers set out to determine whether inter-lab variation stemmed from intrinsic differences or from heterogeneity in the products submitted to those labs. To do this they analyzed a large dataset from Washington state’s seed-to-sale traceability system and looked at the distributions of total reported THC and CBD levels across the six largest labs by data volume in the state.

The state of cannabis analysis

From recreational cannabis products to cannabis grown for federally-sanctioned research to that found on the black market, there is a great potential for discrepancy in the cannabinoid content of available cannabis products. Standardized procedures have yet to be adopted within many labs and there is even a growing controversy on whether labs are measuring and reporting cannabinoid content inaccurately on purpose. Indeed, many recent media reports have claimed labs are overestimating the THC content of cannabis products - so-called THC inflation - and high-profile suspensions of state-licensed testing facilities have only further raised accuracy concerns.

Further to this issue, it is widely regarded by industry professionals that cannabis plants fall into three general chemotypes based on genetically-constrained THC: CBD ratios. Most commercial cannabis is categorized as belonging to chemotype 1 (THC-dominant and light on CBD), while chemotype 3 products have the opposite cannabinoid weighting (CBD-dominant and light on THC) and chemotype 2 is considered a hybrid chemotype with a THC: CBD ratio somewhere between the other two.

However, the general agreement over these classifications shouldn’t be confused with an approval of the more popular commercial categories: indica, sativa, and hybrid. These categories are predominantly quoted within the communities of recreational users rather than those of academia or industry, despite supposedly reflecting the same cannabinoid profiles. Indica, for example, is understood within the recreational community to have a higher CBD content, while a hybrid’s ratio is thought to be a mixture of both indica and sativa.

Testing the labs’ results

To achieve their aims, the researchers first requested the public records for all test results registered with the Washington State Liquor and Cannabis Board (LCB), the state agency that regulates cannabis sales. These records included vital data such as cannabinoid profiles, grower and laboratory information, and the test dates for over 300,000 profiles. To focus their results, the team only analyzed data from two product categories: flowers and concentrates.

Following analyses, the team observed clear differences in reported values of both THC and CBD content across the Washington labs. For example, the median total THC content for chemotype I flower products ranged from 17.7% to 23.2% (average THC content is understood to be around 20%) between the labs reporting the lowest and highest THC levels, respectively. But these varying content levels didn’t appear to be due to random miscalculations. Indeed, the labs that reported the highest levels of THC for chemotype I products also reported the highest levels of CBD for other chemotypes, which indicates a systematic tendency for certain labs to overestimate all cannabinoids levels.

When it came to quantifying commercial “strains”, hybrids were found to have higher mean levels of THC compared to indicas and sativas, but aside from that, the distributions of THC and CBD content among indicas, sativas, and hybrids all overlapped considerably. Final analysis showed that the indica/sativa/hybrid classification system accounted for only about 1% of the relative variability in THC content.

The researchers’ recommendations

Ultimately, the researchers’ conclusions point to ongoing, systematic characteristics within Washington labs that repeatedly skew cannabinoid analyses. This result is therefore in agreement with the wider claims of ‘THC-inflation’, at least with regards to certain labs. Thus, in the absence of federal regulations, the team firmly recommend that state regulators should implement universal testing standards for cannabis labs. As the researchers point out, such stringent standards are already in place for labs that analyze drinking water and evidence from crime scenes. Implementation in commercial and medicinal organizations, therefore, is within reason.

The team even propose three practical steps towards this goal:

1. Firstly, they recommend that cannabis labs should receive third-party accreditation of compliance with International Organization for Standardization (ISO) guidelines, just as other testing facilities are required to possess.

2. Secondly, a standardized cannabis testing protocol should be created, and it would be a requirement for labs to adhere to it.

3. Thirdly, states should introduce regular “round-robin” audits, which would consist of a blind sample being sent for testing across various labs and the results being analyzed by the state to check for discrepancies.

With regards to the state of cannabis classifications, the researchers concluded that there were no substantial differences in the THC or CBD content between flower samples labeled as indica and sativa. However, these results may not be a complete discredit to the terminology. A major limitation of the study was its focus on the Washington traceability dataset, which did not include measurements of other phytocannabinoids or terpenes. It still remains a possibility that indica and sativa samples do differ systematically in their full phytocannabinoid or terpene profiles, which may grant their differentiation merit.

Thus, the researchers proposed an additional recommendation for the future of the field: to organize cannabis products based on computational analysis of large-scale cannabinoid and terpene datasets - a proposal that could help lead to a more accurate classification system than the colloquial names predominantly used today. This wider data collection and terminology could help users become better informed about the cannabis they are consuming. However, incorporating such data would first require the accurate lab testing standards that the researchers are also advocating.


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