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Proficiency Testing for Cannabis & Hemp Labs

An overview of PT, key benefits, how to prepare, and recent trends

Rachel Muenz

Rachel Muenz, senior digital content editor for Lab Manager, can be reached at

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Regulations for cannabis and hemp products vary from state to state and are constantly changing in the US. A key challenge for the industry is consistency in analytes tested, test methods, and standards. Proficiency testing (PT) programs for cannabis and hemp labs provide an important step toward standardization and consistency. 

What is proficiency testing? 

Simply put, PT is a set of experiments that evaluate how well a lab performs a specific set of tests against known standards. 

“Essentially, a proficiency test is any activity undertaken by a laboratory to provide evidence that they are ‘proficient’ to perform specific measurements and/or identification,” says Kirsten Blake, vice president of Emerald Scientific, a company that provides proficiency tests to the cannabis and hemp testing industry. The company also runs the Emerald Test™ inter-laboratory comparison (ILC) proficiency test program for hemp and cannabis labs, which runs twice per year. ILCs involve evaluating a number of labs’ testing abilities through the same proficiency test, and then comparing each lab’s performance to that of the other participating labs. 

The International Organization for Standardization (ISO) standard ISO/IEC 17043:2010 lists the general requirements for PT, defining it as “the evaluation of participant performance against pre-established criteria by means of inter-laboratory comparisons,” Blake adds.  

Proficiency tests are common for labs in other industries such as food and beverage, environmental, and clinical. Labs providing test results under ISO/IEC 17025 are expected to provide evidence of proficiency as part of the accreditation process. For cannabis and hemp labs, such tests evaluate their ability to perform quality assurance testing, or research and development analyses on flower, oil, and many other cannabis or hemp products known as matrices, Blake explains. The tests cannabis and hemp labs usually run include: 

  • Potency
  • Chemical residue or pesticide testing
  • Residual solvent analysis
  • Terpene testing
  • Heavy metals testing
  • Microbial and pathogen analysis  

What does PT for cannabis and hemp labs involve? 

For labs in many different industries, PT programs involve a known sample being delivered to them for analysis, which “may be in the form of an individual blind PT or as a part of a larger study,” Blake says. That sample is made specifically to meet the criteria needed for whatever is being tested by the lab. 

“Overall, we see laboratories who participate in proficiency tests or similar programs regularly tend to be more successful and exhibit improved performance overall.”

“For an inter-laboratory study, typically, the sample to all participants is from the same batch and delivered on the same day and under similar conditions,” Blake says. “From the moment of delivery, the sample should be handled appropriately. The sample is then analyzed within a specific time frame and results reported.” 

Those results are evaluated by the manufacturer of the ISO/IEC 17043 PT and can be graded by either consensus mean or known value, Blake adds. Once that evaluation is complete, depending on the type of PT program, a report summarizing the results is created. For labs participating in an ILC, that report includes how they performed compared to their peers. 

Are proficiency tests required by law? 

Because the requirements and regulations for cannabis and hemp testing vary so widely between states, not all regions require labs to do proficiency testing. However, if labs wish to be ISO/IEC 17025 accredited, they must take an annual PT for each area of analysis, provided PTs are available, Blake says. 

She adds that even though PT is not required in all areas, the cannabis and hemp industry is “seeing a positive trend of labs seeking ISO/IEC 17025 accreditation even in markets where this is not yet required.”  

Why is proficiency testing important? 

PTs are crucial to ensuring the safety of people consuming cannabis products. In the earlier days of the cannabis industry, some labs either knowingly or unknowingly, due to lack of knowledge, provided false quality product reports so consumers didn’t have an accurate picture of the safety or potency of the products they were buying, Blake says. 

“This still persists as an issue in the industry and, while PTs don’t test for ethics, they can at least test for a lab’s competency in providing accurate results,” she says. 

She adds that PT also reduces product liability, ensuring the cannabis or hemp product complies with local and state regulations, which prioritize consumer safety. Making sure a lab is performing quality assurance tests accurately ensures cannabis products are meeting these regulations, thus reducing the potential for product recalls and lawsuits. 

In addition, participating in PT programs boosts customer confidence in the lab’s work and can help labs improve their performance, Blake adds. 

“We have years of data providing evidence that the laboratories have consistently improved their performance in all areas of cannabis analysis as they continue to take on more challenging and difficult matrices,” she says. “Overall, we see laboratories who participate in proficiency tests or similar programs regularly tend to be more successful and exhibit improved performance overall.” 

How do labs best prepare for proficiency testing?

There are practice tests available for most PTs to help labs get ready.  

“I do recommend becoming familiar with the tests and directions prior to taking a blind PT as there can be some variability between actual lab samples and test samples due to legal compliance constraints,” Blake says. “Additionally, practice tests can play an important role in day-to-day internal [quality control] QC operations and these can also be used to confirm an employee’s analytical skills.” 

The most important thing labs can do to prepare for PT is to develop a strong relationship with their auditors or agencies they are regulated by, as rules may be interpreted differently from one month to the next, Blake advises. 

“It is best to develop a good rapport with regulatory contacts early to avoid costly misunderstandings,” she says. “This is easier in some states than others.” 

What are recent trends in proficiency testing for cannabis and hemp labs? 

As for recent changes, some states are now requiring that all analytes must be present in PT samples, Blake says, adding that, “some go even further to require the sample to be ‘in matrix’ such as flower or oil, which introduces other complexities.” 

For example, when doing PT for pesticide tests, all regulated pesticides that labs test for must be included in the PT sample.

“For some states this could be over 68 analytes,” Blake says. “These don’t all behave well nor will they remain stable when they are all together, so we must then offer several samples for stability purposes to meet this specific need. This creates a very cost prohibitive hurdle for both labs and test manufacturers.” 

In other trends, organizations such as universities, AOAC International, and the National Institute of Standards and Technology are now looking into PT for cannabis and hemp, while others are starting to analyze the PT data generated from cannabis and hemp testing labs so far, Blake says. She adds they’ve also seen an increase in cultivators and manufacturers adopting PTs and expects this trend to continue as the industry moves toward adopting processes such as good manufacturing practices (GMP). Since testing is a crucial part of meeting GMP requirements, this will increase the demand for quality analytics, Blake says. 

If labs hope to keep providing high-quality testing of cannabis and hemp products and remain competitive as the industry continues to grow, participating in PT programs will likely play an important role in their continued success.

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