6 rapid tests approved to detect yeast and mold in cannabis

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Validated rapid testing for total yeast and mold in cannabis is now a reality, thanks to six new approvals of tests applying technology from the food and environmental sectors.

Traditional methods for establishing total yeast and mold in a cannabis sample generally require five to seven days. Rapid kits can reduce this time by 50% or more.

AOAC International, an independent scientific nonprofit known for publishing standardized, chemical analysis methods, on June 4 approved six rapid tests kits for total yeast and mold in cannabis flower.

The approvals come after AOAC International launched an emergency multi-laboratory validation investigation in response to complaints of “moldy” cannabis.

These approved tests are now headed to the AOAC International Official Methods of Analysis compendium:

  • Neogen Soleris Direct Yeast and Mold (48-72 hours)
  • 3M Petrifilm Rapid Yeast and Mold Count Plate (48-72 hours)
  • 3M Petrifilm Yeast and Mold Count Plate (3-5 days)
  • BioMerieux Tempo Yeast and Mold Count Plate (72-76 hours)
  • Nissui Pharmaceutical Company Compact Dry YMR Rapid Test Dish for Mold Yeast (48-72 hours)
  • MilliporeSigma SimPlate Yeast and Mold Color Indicator (56-72 hours)

In all cases, the methods are proprietary and were either validated for cannabis (THC > 0.3%) flower matrix exclusively or were previously validated in food and/or environmental matrices and then underwent validation for matrix extensions.

The AOACI announcement states, “Now these kits can be recognized by accreditation bodies as validated for dried cannabis flower …”

Why should accreditation bodies be concerned about validated test kits, and will it impact accredited laboratories?

Method validation and method verification are often, and incorrectly, used interchangeably in attempts to vet a new method. The purpose of method validation is to ensure the method developers have created a new test method that meets the intended purpose.

In all of the cases in the study, developers had to ensure the methods fulfilled specifications in the Standard Method Performance Requirements for total yeast and mold.

For example, to meet the requirements, a method must demonstrate exclusivity and inclusivity and have a 50% probability of detection.

Typical single-laboratory validation protocols require characterization of 10 to 12 parameters.

After that, multi-laboratory validation studies are sought for objective evidence that the method is fit for use and is reproducible.

AOAC International sent 10 test kits to six independent laboratories to obtain objective evidence that the kits were fit for intended use and met all the analytical performance requirements.

When it is necessary to extend the applicability of a method, partial validation studies recharacterize only relevant parameters.

Method verification meets different requirements.

Before a laboratory can use a standard test method – for example, any AOACI-validated total yeast-and-mold test kit – it must demonstrate correct implementation of the standard using its own resources.

This makes short work of the task and positions the laboratory to quickly adopt standard methods without needing to develop and validate in-house methods.

In all cases, ISO/IEC 17025-accredited laboratories must provide objective evidence that their test methods have been either adequately validated or appropriately verified before working on customer samples.

For labs that employ standard methods that undergo multi-laboratory validation studies, accreditation bodies limit their investigation to objective evidence that the laboratory has the resources and technical competence to correctly implement the standard.

It is exciting to see multi-laboratory validation studies conducted by an independent source using cannabis (>0.3% THC) matrix.

Of the 10 test kits evaluated, six are currently approved and several others are in queue for further evaluation.

As these become AOAC International standard methods, laboratories will need to provide objective evidence of method verification to their accreditation bodies, eliminating the need for in-house method development.

Susan Audino, who holds a doctorate in chemistry, is a chemistry consultant and instructor for the American Association for Laboratory Accreditation. She is based in Ohio.