Did the Michigan Marijuana Regulatory Authority (MRA) ban molecular methods for microbial testing?

No, the MRA did not ban all qPCR tests for cannabis. In this article we aim to clarify some recent misinformation.

Updated June, 2021

Did the Michigan Marijuana Regulatory Authority (MRA) ban qPCR?

  • No. In January of 2021, the MRA issued a statement  which temporarily "disallows the sole use of molecular methods such as qPCR for the quantification of total yeast and mold (TYM)”, based on preliminary data from the AOAC’s Emergency Response Validation (ERV) to address the MRA’s concerns over TYM testing. However, the MRA said it will reevaluate this decision as new information is gleaned from the ERV study. Unfortunately the MRA’s decision to change the requirements based on an incomplete study and in "an abundance of caution" has caused significant disruption to the sector.  
  • The January 2021 statement provides guidance for how Michigan labs that currently use qPCR should test for TYM going forward.  
  • It should be noted that the AOAC's ERV, and subsequent draft SMPR, aims to evaluate TYM methods on cannabis flower only. The MRA's statement does not specify a matrix in their temporary disallowment of molecular methods, but it appears that molecular methods for testing marijuana infused products (MIPS) have been temporarily disallowed as well. 

Does the MRA require labs to use AOAC certified methods?

  • No. The MRA does NOT require a method to be AOAC certified. However, they make it very difficult to select a method outside of those that have received AOAC certifications. There are only AOAC SMPR's established for a select few targets and in some cases, only for certain matrices (flower). Search AOAC certified methods here.
  • Due to the confusion with their messaging in recent months, the MRA has published a letter to all licensed laboratories in Michigan on April 16th, 2021. In it they clarify the following:
    • All safety compliance facilities are required to employ the use of validated methods for all testing required by the agency in accordance with R 420.112(4)(b).
    • Additionally, R 420.305(2) requires a laboratory to use analytical testing methodologies for required safety tests to be validated by an independent third party, and are subject to monitoring on an ongoing basis. In the absence of reference to compendia or published methods, Appendix K (or J where appropriate) of the AOAC must be published in full.
    • When available, the standard method performance requirements (SMPRs) help to clarify the requirements of the validations. If the laboratory is running a method that has been appropriately validated or references a published method, the validation is expected to meet the targets (e.g. % recovery) outlined by the SMPRs. If the laboratory is seeking to pursue validation, either independently or with the assistance of a vendor, they must adhere to the published required analytical criteria.
    • Changes to the Technical Guidance document are issued twice a year, with the expectation of compliance to the requirements outlined in the guide within 6 months from the date of publication. Version 3.0 of the Sampling and Testing Technical Guidance for Marijuana Products was released on February 11, 2021. Therefore, safety compliance facilities must comply with the changes outlined in this guide on or before August 11, 2021.
    • All laboratories will receive updated method approval forms indicating any outstanding deficiencies. The laboratory is responsible for contacting their assigned LSS with any questions well in advance of the August 11, 2021 deadline for implementation of all changes.

What is MGC doing to address the situation with total count tests in Michigan?

Are there any changes coming to the TYM or TC assay?

  • We have not made any changes to the design of our TYM qPCR assay. Inclusion and exclusion testing has confirmed that our primer design is robust.  
  • Our new TYM protocol includes improvements  to our extraction method so we can lyse open more cells, improve genomic DNA recovery, and improve concordance with plating when compared with industry CRMs. However, the aforementioned challenges with designing an assay to compare to plating are numerous. 
  • There is no change forthcoming on Total Coliforms as the AOAC has not published an SMPR for it. Once they do we will submit our assay to the AOAC for certification.

Does this mean my Total Yeast and Mold results have been wrong?

  • Any claims of contaminated samples in Michigan dispensaries are unsubstantiated and reckless.  There is an ongoing scientific debate amongst Michigan's cannabis testing laboratories and regulators over the different technologies used to detect yeasts and molds in cannabis (See the AOAC ERV Study). However, Michigan officials are on record as saying there is no public safety concern.
  • Our method validation for TYM is more robust than any on the market. The Cq/CFU equation in our validation document was generated with samples spiked with live organisms. Those organisms were chosen because they are well documented to be found on cannabis, or were well studied yeasts/molds,  and in most cases were used in 3Ms own method validation.

Problems Comparing qPCR to Plating

  • The issue that we believe precipitated the MRA's actions started with a new NSI CRM for TYM proficiency testing.  This PT was developed for culture based methods and does not produce qPCR results that are consistent with plating using MGC's SOP for total count tests.
    • Our own investigation found that the NSI CRM for TYM (the emerald test panel) was  ground to a fine powder, frozen, and contained cryopreservatives that are known to inhibit gDNA extraction.
  • In general, this is not surprising since plating for “total” counts are inherently flawed and not comparable to qPCR results. Not all yeasts and molds grow in culture plates, but are picked up in qPCR. Bacteria often grow in TYM  plates, but our assay is designed to exclude the bacteria. We write about this extensively in our help center: