The AOAC INTERNATIONAL Guidelines for Laboratories Performing Microbiological and Chemical Analyses of Food, Dietary Supplements, and Pharmaceuticals, An Aid to Interpretation of ISO/IEC 17025:2017 was created by the Analytical Laboratory Accreditation Criteria Committee (ALACC) to provide a section-by-section interpretation of requirements.
ALACC is a multinational group of experts from varied scientific disciplines and industries, and part of AOAC’s Technical Division for Laboratory Management (TDLM).
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Section 6.4.4. of the Guidelines states that reagents, reagent solutions, sample solutions, and internal reference materials (including certified reference materials (CRMs) used as internal reference materials) shall not be used past their expiration date without recorded verification that they are still suitable for use. Media and CRMs cannot be used beyond their expiration date. Note: Expired CRMs can be qualified as Reference Materials (RMs).
Question A: When can an expired CRM be used?
Answer: A CRM is an RM characterized by a metrologically valid procedure for one or more specified properties, accompanied by a reference material certificate that provides: 1) the value of the specified property, 2) its associated uncertainty, and 3) a statement of metrological traceability. When a CRM expires it loses a link to its uncertainty and traceability but still may be sufficiently homogeneous and stable with respect to one or more of its specified properties. Thus, a CRM that has passed its expiration date can still be used as a QC or as an RM if it is used in a manner that does not require the application of these two lost attributes as long as it is evaluated and re-qualified for suitability.
Reference: ISO Guide 80:2014 , Guidance for the in-house preparation of quality control materials (QCMs) https://www.iso.org/standard/44313.html
Question B: When can an expired media be used?
Preparation instructions on the Violet Red Bile agar bottle indicates the media is to be used within the same day it is prepared, and preparation instructions on the Bismuth Sulfite agar bottle indicates plates shall be used within 48 hours of preparation. Can the laboratory assign its own expiration date based on data demonstrating the media is still viable after these times on the media bottles, or does the requirement that media cannot be used beyond its expiration date apply to the expiration date based on the manufacturer preparation instructions of the media?
Answer: While clause AOAC 6.4.4 states that ”…Media…cannot be used beyond (its) expiration date,” there is no language in either ISO/IEC 17025: 2017 or the AOAC criteria that defines to which expiration date the requirement is referring. In keeping with the risk and opportunity based approach of the ISO/IEC 17025: 2017 standard, it is “the laboratory which is responsible for deciding which risks and opportunities need to be addressed” and per clause 8.5.3, “actions taken to address risks and opportunities shall be proportional to the potential impact on the validity of laboratory results.” Therefore, the laboratory can risk assigning its own (longer expiration dates) to prepared media, as long as they can provide evidence that the media performs properly for the length of the expiry assigned. This includes quantification on VRB agar and growth/selectivity on BS agar.
Section 8.8.1. of the Guidelines states that internal audits of laboratory information management systems shall be conducted at least once per accreditation cycle. What information is required to satisfy this requirement?
Answer: The laboratory is required to audit the acquisition, transfer and data storage process in the LIMS, along with permissions for access to the various data to ensure only authorized personnel can access the different parts of the LIMS.
In the 2018 AOAC Guidelines stated that if there can be an acceptable alternative to measuring the mass of water as a means of verifying the accuracy of volumetric delivery devices: mechanical pipets, mechanical burets and liquid dispensers:
Specifically this concerns bottle top dispensers. “We verify our bottle top dispensers by dispensing the liquid needing measured (usually an acid) into a class A cylinder on the day of use. If the volume is accurate, the measurement is documented and the dispenser is then used freely until the volume is changed or until next day of use. The question is, can this volume check method be considered an acceptable alternative to weighing on a balance as we are not wanting to put water through our acid dispensers?
Answer: An acceptable alternative to weighing the mass of liquid delivered by a bottle top dispenser would be through measuring the dispensed volume of liquid. It is up to the lab to ensure the alternative to weighing is suitable for its intended use.
Is it acceptable to place information about a method, such as acceptance criteria for quality control materials, in the LIMS?
The requirement states that a calibration is required when a balance is “moved to a different location or after repair”. However this has created some confusion as to whether there is a certain magnitude of the move or repair, that if exceeded would trigger the need for a calibration.
Answer: A calibration is required when there has been a significant move (one involving packing and transport) to a different location or after a repair that requires significant disassembly and that produces a significant risk to the accuracy of measurements. A move to another lab bench or a minor repair would not necessarily trigger the need for a calibration.
Section 7.7.1, ALACC notes state, “When testing for pathogens or select agents, a quality control material that contain a surrogate analyte may be used.” How does my lab determine what surrogates to use and if we are using an appropriate surrogate?
Answer: The laboratory typically uses a surrogate when the pathogen in question is deemed too risky to use in house with each batch of samples. A risk assessment is done to determine whether a surrogate is needed or if the lab can adequately accommodate the target pathogen.
The surrogate analyte shall be sufficiently characterized for the properties it is being used to confirm in the test. There may be a need to use more than one surrogate to confirm a pathogen test from primary enrichment through screening and confirmation. The laboratory shall retain records demonstrating the surrogate(s) used has(have) been sufficiently characterized and meet the needs of the lab.